>>> Can it be a certification issue ?
It could be a communication issue. I found some older discussions where issues with the same error message were solved by rebooting the ESXi host. If this is currently not an option for you, maybe restarting the management agents on the host will already help. Just a guess, but maybe worth a try!?.
I moved the discussion, because I think you may get more feedback for this issue in this community. If you want me to move the discussion back to the original place, please let me know.
André