SQL 2005 monitors not working after SP4

SQL 2005 monitors not working after SP4

Hello, we have two servers with Microsoft SQL server 2005 STD, we had configured a few SQL monitors and was working propertly, but after aplying SP4 to SQL, the SQL monitors stop responding and the data for this monitors are N/A.
I have already try the following:
- To rediscover server
- Delete server and add again (the new server is not automaticaly detected as SQL and therefore doesnt add automaticaly the SQL monitors), add manualy the SQL monitors - WMI credentials are tested, Monitors-->Performance Monitors-->Add Monitors--> MSSQL monitors.
But monitors are still N/A, if I try to test a monitor I get this error:
The Monitor did not respond to the test request
Summary
Device Name xxxxxxx
Monitor Name Cache Hit Ratio
Protocol
SNMP
 
 
Thans a lot for your help

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