503 error: "mod_lsapi: Connect to backend failed: connect to lsphp failed: 110"

Symptom

A site shows a 503 error, and an error message similar to the following may be found in the Apache error log.

[Thu Apr 21 13:15:15.520133 2022] [lsapi:error] [pid 1866056:tid 47371331020544] [client 203.0.113.2:43842] mod_lsapi: [host domain.tld] [req HEAD / HTTP/1.1] Connect to backend failed: connect to lsphp failed: 110

Description

The error occurs when the PHP version specified in the domain's userdata file doesn't match the PHP version in the site's .htaccess file. Changing the domain's PHP version and then changing it back will correct this issue.

Workaround

1. Log into WHM as the 'root' user.
2. Navigate to "Home / Software /MultiPHP Manager."
3. Click the "User Domain Settings" tab.
4. Locate the domain encountering the 503 error.
5. Toggle the "Inherit" checkbox.
6. Click the "Apply" button.
7. Wait until the "Success" message is displayed.
8. Toggle the "Inherit" checkbox.
9. Click the "Apply" button.

Additional resources

MultiPHP Manager for WHM: User Domain Settings tab