Test connection to Plesk from WHMCS fails: Unable to find appropriate manager for this version of Panel in WHMCS

Symptoms

Test connection to Plesk from WHMCS fails:

PLESK_INFO: FAILED: Error code: 0. Error message: Unable to find appropriate manager for this version of Panel. Plesk should be at least 8.0 version

Cause

Possible reasons:

1. WHMCS uses HTTP connection instead of HTTPS to connect to Plesk API.

2. The option Ability to use remote API is disabled for the reseller in Plesk.

3. The server where WHMCS is installed is not authorized to run WHMCS.

Resolution

Make sure that the following requirements are met:

1. The option Tick to use SSL Mode for Connections should be checked in WHMCS.
   
   

2. When reseller credentials are used for connection, the option Ability to use remote API should be checked for this reseller at Plesk > Resellers > John Doe > Customize > Permissions tab.

3. The domain should be authorized to run WHMCS. This can be checked with the WHMCS License Verification tool.