One plus 3t Wifi disabled

[redx64]

Few days after upgrading to Oxygen stock pie , i cannot connect to any Wifi. Ive tried public wireless points and different AP and the answer is always the same.

Now I have reset my phone to Oxygen Os 5.0.8 and its still the same. It can find Wifi APs but cannot connect to them.
Everything else works including GPS, Bluetooth, Data and even Wifi hotspot

Any suggestions?

 

[redx64]

I just found a possible hint. If I place the phone very close to the router, almost touching it. The wifi connects.
Possibly an antenna issue? Does anyone know of changing the wifi antenna