You mentioned re-flash the USB - so you are booting from USB and not SD is that right?
If so, may find solution in this thread (the image is for SD so minor change needed for USB) - Flashing and using generic USB for PiFi install - #6 by Scouter
You mentioned re-flash the USB - so you are booting from USB and not SD is that right?
If so, may find solution in this thread (the image is for SD so minor change needed for USB) - Flashing and using generic USB for PiFi install - #6 by Scouter