I've never had a Whistler that I couldn't program that wasn't defective.
That said, I would start over from scratch.
1. Try weather, if you receive something, keep going. If not, you probably have a defective unit or a bad antenna.
2. Try a limit search of 154.325 to 158.73. Make sure that NXDN, DMR, P25, X2 and Zeromatic are checked with squelch set to search. See if you get anything.
Is it possible that you're too far away?
These are the notes on the Fannin County site:
(2/24) Sheriff and Fire has recently switched to NXDN 6.25 KHz conventional, no encryption at this time. If anyone can find the RAN and talkgroups (if in use), please submit. If anyone knows if the former VHF analog is still in use, please advise.
(2/21/24) Fire is still operating on analog.