Plesk Installations screen under Cloud Infrastructure > Plesk in VPS menu does not show any instances.
The behavior is recognized as a software issue with internal ID CCU-16914 (Plesk Installations list cannot be loaded). The issue appears in case of a large amount of instances (>300).
As a workaround, it is possible to list the instances at Applications > Plesk in VPS Panel > Instances.
Contact your Technical Account Manager or Pooled Technical Associate Team (firstname.lastname@example.org) in order to trace the current status the issue.