My cable company made me switch to a new modem.
Everything else with my Pi 3 FlightAware feeder remained the same.
I correctly entered the new modem name and password on the SD card.
My feeder was no longer recognized by FlightAware.
Only after I deleted my feeder and tried again was it recognized by FlightAware. It was recognized as a completely new feeder. Only the wifi modem had changed.