Testing agent credential fails on Agent > Set Credential page, but credentials have been confirmed to be valid.
Kaseya Agent service was running as a user, when it should run as SYSTEM account.
Open Windows services manager (services.msc), go into properties of "Kaseya Agent" service, and ensure it is set to run as local system (see below). Then restart the service, check in Task Manager that its now running as system, and re-try the credential test.
Kaseya VSA - all versions