I have been having this issue. Did not want to factory reset as, to be honest, I am quite sick of this phone and having to do it. It ties in with this thread on the Acer Community as I posted my fix there but the mods say that it breaks the rules. Strangely I could not see a rule that says you cannot help people fix their issues but I might have missed it ! 
This is my solution:
I am afraid that you will have to have something similar to root browser installed for this to work
Navigate to:
/data/misc/dhcp/
and you will see a list of files that look like the leases for the DHCP. I chose the latest time/dated one and deleted (I suggest you rename or move yours) it and it is called:
dhcpcd-wlan0.lease
I then connected very quickly to the routers that I couldn't before.
It's worked for me, I really hope it does for you as I know the frustration for this.
Please take the time to say if it did/didn't work.
Not sure how sticky this deletion is, but if I have to repeat it then so be it.
This is my solution:
I am afraid that you will have to have something similar to root browser installed for this to work
Navigate to:
/data/misc/dhcp/
and you will see a list of files that look like the leases for the DHCP. I chose the latest time/dated one and deleted (I suggest you rename or move yours) it and it is called:
dhcpcd-wlan0.lease
I then connected very quickly to the routers that I couldn't before.
It's worked for me, I really hope it does for you as I know the frustration for this.
Please take the time to say if it did/didn't work.
Not sure how sticky this deletion is, but if I have to repeat it then so be it.
