Plesk shows 502 Bad Gateway error and service sw-engine is marked as stopped

Symptoms

• Plesk shows 502 Bad Gateway error;

• The service sw-engine is not running:

  # service sw-engine status
  ● sw-engine.service – Startup script for Panel sw-engine
  Loaded: loaded (/usr/lib/systemd/system/sw-engine.service; enabled; vendor preset: disabled)
  Active: inactive (dead) since Mon 2018-03-26 21:57:49 +07; 5min ago

Cause

sw-engine service is stopped. This may occur if upgrade attempt was unsuccessful or it was stopped manually.

Resolution

For Plesk Onyx 17.8

1. Click Open Repair Kit and log in with Plesk admin credentials.
   
2. If it was successful, try starting sw-engine service by clicking Restart Processes
   
3. If it was successfully started, click Log In to Plesk button
   

For other Plesk versions

1. Connect to the server via SSH.

2. Start sw-engine service:

   # service sw-engine start

   Or start psa service:

   # service psa start

Additional info

[HUB] 502 Bad Gateway