Please review McAfee Support Article: KB76736 - ePO 5.0 supported products
This lists the supportability requirements for all managed products, towardst he end of the list you'll see:
"ePO 5.0 support for MEG 7.6 and MEG 7.5 will be added in a patch after the MEG 7.7 release."
For any further information you would need to discuss this with the MEG team rather than ePO.
Moved to MEG group.
As noted by Rackroyd above, MEG 7.x does not currently support management with ePO 5.x. That support is due in a future version of MEG, probably 7.7. In the meantime, you will need to run ePO 4.5 to manage your MEG appliances.