Scanning for WordPress installation was performed with the following error:
Subscription "example.com": This site is not a webspace.
The "example.com" does not have hosting, its hosting type is "Forwarding", so it is indeed not a webspace.
Such behavior is considered to be a software issue that should be fixed in further Parallels Plesk updates. The issue id is PPPM-1648 .
Ignore the message.