From SAP:
Dear Fadzly,
I have checked the issue and I think there is a misunderstanding here for creating the user manually.
Usually the monitoring user, which usually has the name SAPMonitor or <(><SID>_SAPMonitor (in your case PRD_SAPMonitor) is created
automatically by the initiating process. The user, what needs to be created is only a temporary user with administration priviledge. You can use here an already existing
administrator e.g. the user sa, which has SQL Server Authentication possibility.
For more details please check the SAP KBA:
1904412 - DBA cockpit connection XXX cannot be established
I am suggesting also to upgrade the SAP_BASIS component to the latest version, because it contains Monitoring related corrections like:
1963503 - Objects erroneously dropped and created in the 'dbo' schema due to an error
Please update also the kernel and DBSL module to the latest patch level.
thank you for your feedback in advance
best regards
Sándor Szalina
SAP Product Support