You might encounter the following error while registering a new server in PG Admin.
Instance '<Server at <guid>>' is not persisted.
The issue is mostly due to uninstalling and re-installing PG Admin or installing a different version of PG Admin.
The resolution would be the following.
- Close PGAdmin
- Browse to
C:\Users\<your user>\AppData\Roaming - Delete the folder
PGAdmin - Open PGAdmin
This will resolve the issue