Unable to add Docker Proxy rules in Plesk, no container is displayed

Symptoms

• When trying to add a new Docker Proxy rule in Plesk at Domains > example.com > Docker Proxy Rules, no container is shown even if it's running in the Docker extension:
  

Cause

Docker container has Automatic port mapping enabled.

Resolution

1. Log in to Plesk;
2. Go to Docker > Container-name > Settings:
   
   
3. Uncheck the  Automatic port mapping setting and specify fixed ports: