"Sim Empty" and cannot make calls after upgrade
I am in exactly the same situation, Wileyfox upgrade to Nougat, and have not found a good fix.

However what has worked (to a point) is as below:


Turn off remove sims and battery for at least 5mins
Insert 1st SIM, battery and reboot.
At this point 1st Sim should be recognised.
Turn off remove battery for 1-2mins.
Insert 2nd SIM, battery and reboot.
Both Sims should now be recognised.
Set and check preferences for Calls, Data, SMS etc.
Leave phone on!!!! &lt;- A new problem


As soon at the phone is turned off and on again its back to square one :-(.

I guess it could be a specific problem with Cyanogen >>> Nougat, and the firmware handling 2 sims on boot up.

For reference my Sims are o2 and EE.