When open studio it shows error "a working monitor service not found"
Get-monitorservicestatus, we get unknown the object in monitordata.getschemaversion has no execute permission
At the same time, Director show can't retrieve data 
End user connection will not be impacted at the same time and if DDC is not restart, studio is still open, Administrator can still manage on studio

1. Expand CitrixMonitoring database->Programmability->stored Proccures, right click properties of Monitordata.getschemaversion, click permisions

2. Click schema permissions, it should include the following permission, if it is not please ask DBA to fix the permission issue in database first 

Problem Cause

DB issue