NSpanel Pro dropping out

I have the NS pro set up with several zigbee devices.
Every now and then I lose all zigbee devices from the ewelink app but the NS pro continues to show. If I try to interact with it via the app then it says its off line.
This will continue for up to a week. Then suddenly come back and be stable for another week or so.
I check my router and found the NS pros IP address showing as connected.

Anyone offer any suggestions as to what may fix this issue?