Sometimes on Plesk a login issue causes the left panel of server management links to not appear. So you have the main screen of subscriptions/web sites appearing only. A simple server restart can usually fix this. Please claims the issue was fixed in v 12.
When installing a new WordPress site manually – due to migration from another server using Duplicator for example, you can rescan for WordPress sites to allow control of the site via Plesk see more here from Plesk FAQ.