# Troubleshoot Lightsail Connect errors
<a name="amazon-lightsail-troubleshooting-connect-errors"></a>

This guide explains the error codes you might see when connecting to a Lightsail instance through the browser and what you can do to connect again. Find the error code you encountered in the list below, and work through its steps.

## 512 (SERVER\_ERROR)
<a name="connect-error-512"></a>

**What it means:** An unexpected error occurred and the connection could not be completed.

**Likely cause:** An intermittent network or internet issue, or a connection reset.

**What to do:**
+ Ensure your internet connection is stable.
+ Refresh the Lightsail Connect session.

## 514 (UPSTREAM\_TIMEOUT)
<a name="connect-error-514"></a>

**What it means:** The connection timed out while waiting for a response.

**Likely cause:** A network interruption during the connection.

**What to do:**
+ Ensure your internet connection is stable.
+ Refresh the Lightsail Connect session.

## 515 (UPSTREAM\_ERROR)
<a name="connect-error-515"></a>

**What it means:** The connection to your instance could not be completed.

**Likely cause:** Your instance is low on resources or still starting up and not ready to connect. It can also happen when your instance's firewall rules block SSH/RDP. For more information about firewall rules, see [Control instance traffic with firewalls in Lightsail](understanding-firewall-and-port-mappings-in-amazon-lightsail.md).

**What to do:**
+ If the instance was recently started or rebooted, wait a short time for the instance to be ready to connect, then try again.
+ Verify your instance's firewall rules allow SSH/RDP from Lightsail Connect.
  + If a required rule is missing, add it by following these instructions: [Add firewall rules to Lightsail instances](amazon-lightsail-editing-firewall-rules.md)
  + Retry the connection after adding the required rule.
+ Reboot the instance following these instructions, then try again: [Start, stop, or reboot your Lightsail instance](lightsail-how-to-start-stop-or-restart-your-instance-virtual-private-server.md)

## 516 (RESOURCE\_NOT\_FOUND)
<a name="connect-error-516"></a>

**What it means:** Lightsail Connect cannot find your instance.

**Likely cause:** Your instance may have been deleted, or there is a temporary problem reaching it.

**What to do:**
+ Confirm the instance still exists in the Lightsail console. If it was deleted, connect to a different instance.
+ Wait a moment, then try connecting again.
+ Check your instance's state in the Lightsail console. If it is still starting, wait until it is running, then try again. If it is stopped, start it and wait until it is running before connecting. [Start, stop, or reboot your Lightsail instance](lightsail-how-to-start-stop-or-restart-your-instance-virtual-private-server.md)
+ Reboot the instance, then reconnect.

## 519 (UPSTREAM\_NOT\_FOUND)
<a name="connect-error-519"></a>

**What it means:** Lightsail could not reach your instance.

**Likely cause:** The instance is not reachable, most often because it is still starting up or is not yet responding.

**What to do:**
+ If the instance recently started or restarted, wait a few minutes for it to finish starting, then try connecting again.
+ Confirm the instance is running in the Lightsail console.

## 521 (SESSION\_CONFLICT)
<a name="connect-error-521"></a>

**What it means:** Your session ended because another session took over. Only one RDP session is allowed at a time.

**Root cause:** A second RDP session was opened to the same instance, for example in another browser tab, and it took over from the first.

**What to do:**
+ Close the session you do not want to use, then reconnect in the one you want to keep.
+ Avoid opening multiple RDP sessions to the same Windows instance.

## 523 (SESSION\_CLOSED)
<a name="connect-error-523"></a>

**What it means:** The session on your instance ended, so the connection was closed.

**Likely cause:** Most commonly the instance was rebooted or stopped. It can also be caused by the session being logged off.

**What to do:**
+ If the instance is rebooting or stopping, wait for it to finish, then reconnect.
+ If the instance remains unresponsive, reboot it and try again. [Start, stop, or reboot your Lightsail instance](lightsail-how-to-start-stop-or-restart-your-instance-virtual-private-server.md)

## 524 (UPSTREAM\_NLA\_AUTHENTICATION\_FAILURE)
<a name="connect-error-524"></a>

**What it means:** RDP authentication failed. The password provided was rejected by your instance. You will typically see an "Invalid password" message.

**Likely cause:** The instance password was changed and the entered credentials no longer match.

**What to do:**
+ Re-enter the correct current password for the instance.
  + If you recently changed the password, use the new one.

## 525 (CONNECTION\_DEADLINE\_EXCEEDED)
<a name="connect-error-525"></a>

**What it means:** You reached the maximum amount of time Lightsail Connect allows for a single session, so Lightsail Connect closed the connection to your instance.

**Root cause:** The session reached the connection time limit set by Lightsail Connect.

**What to do:**
+ Reconnect to start a new session.

## 767 (UPSTREAM\_HOSTKEY\_MISMATCH)
<a name="connect-error-767"></a>

**What it means:** The SSH host key presented by your instance does not match the host key we have on file.

**Likely cause:** The SSH host key on the instance changed, for example when keys were regenerated or manually changed.

**What to do:**
+ If you recently made changes to your instance and expected its host key to change, this is expected. In the dialog, choose **Reset record** to update the host key Lightsail has on file; the connection then resumes automatically.
+ If the dialog asks you to try again later, wait a few minutes, then reconnect.

## 768 (CLIENT\_BAD\_REQUEST)
<a name="connect-error-768"></a>

**What it means:** The connection could not be started because the request was not valid.

**Likely cause:** This is usually a temporary or browser-side problem, not something wrong with your instance.

**What to do:**
+ Refresh the browser tab and start the connection again from the instance's connect page.
+ If the instance recently started or changed state, wait a minute or two, then try again. [Start, stop, or reboot your Lightsail instance](lightsail-how-to-start-stop-or-restart-your-instance-virtual-private-server.md)

## 769 (CLIENT\_UNAUTHORIZED)
<a name="connect-error-769"></a>

**What it means:** Authentication to the instance failed. The SSH key presented was rejected by your instance.

**Likely cause:** You might see this shortly after an instance is created, before the instance is ready to accept Lightsail Connect sessions.

**What to do:**
+ If you recently created or started the instance, wait a few minutes, then try connecting again.

## 771 (CLIENT\_FORBIDDEN)
<a name="connect-error-771"></a>

**What it means:** Access to the connection was denied.

**Likely cause:** Usually a transient permission issue.

**What to do:**
+ Wait a moment and try connecting again.

## 776 (CLIENT\_TIMEOUT)
<a name="connect-error-776"></a>

**What it means:** Your browser stopped responding to the Lightsail Connect server, so the connection was closed.

**Likely cause:** The browser throttled or froze the background tab/window, which is common when the tab is minimized or left in the background.

**What to do:**
+ Keep the connection tab active and in the foreground.
+ Reconnect to resume your session.
+ Avoid letting the browser suspend the tab during long sessions.

## 797 (CLIENT\_TOO\_MANY)
<a name="connect-error-797"></a>

**What it means:** You have opened too many concurrent sessions. The maximum is five SSH sessions and one RDP session per instance.

**Root cause:** Opening additional sessions beyond the allowed limit.

**What to do:**

1. Close existing sessions before opening new ones.

1. Ensure you stay within five SSH / one RDP session per instance.