GUPs not working after Management server upgrade

Hi,

Recently, i had upgraded all my managerment servers fom SEP11 RU5 to SEP12.1RU2.
Then I noticed that all my GUPs stop functioning. The SharedUpdates folder on the GUPs no longer gets updates even though the agent was updated.
The SEP Agents on my GUPs and clients are still on SEP11RU5 and MR4.

My Question is that does the agents on the GUPs should have the same version as the management server in order for the GUPs to function ?

Please advise.