Issue with ESX 4.1i to be added in OPManager upgrade to build 8811

Issue with ESX 4.1i to be added in OPManager upgrade to build 8811

Hello,
 
I upgraded OPManager to build 8811 then I tried to add a new esx 4.1i in OPManager.
I configured SNMP and created an account usable in OPManager to get information then ESX 4.1 is added but I got this error message
 
Could not collect data, HTTPS connection may be slow or not responding. Probable reasons are timeout, more connections, invalid username and/or password.
 
Username and password are working fine.
Can you point me in direction that I can check?
 
Best regards
Philippe

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