FGT7060 (v5.6.6) can't be registered into FMG400E (v6.0.4)

Hi,

Does anyone ever try to register FGT 7060E (FortiOS 5.6.6) into FMG400E (v6.0.4)?

Because I have tried and it can't be registered. I have enable ADOM and create the new ADOM for FortiGate 5.6. When I tried to add FortiGate device to FortiManager, error occured "Unsupported device version".

Thank you