Google Play :Error while retrieving information from server. RPC:S-7:AEC-7 ..How can I fix this?

[AC Question]

Google Play :Error while retrieving information from server. RPC:S-7:AEC-7 ....

I have recently bought an Honor 7 phone from China (not yet available in my region). It did not come with Google play, but I installed this from the Huawei app centre.

I have had various tussles getting it all to work but finally it did and I got contacts to sync.

Initially I was able to download from Google play. However, after a while it then started giving me the error above.

I have tried various solutions : logging out of my account, removing and reinstalling the account, killing cache and data in Google play and Google play services and framework, even performed 3 factory resets.

Factory resets seem to temporarily fix it ie by reinstalling Play, but after a while it does wrong again.

This is weird; I can't understand why it would work at all if the phone or firmware is unacceptable to Google, but it does initially and then stops.

Is there anything I can do or am I destined to give up on this phone and return it?

(ps was using previous Android phone with Google play without issue)