2006 Ford F-150 won't shift into 4 high or 4 low

2006 Ford F-150 wouldn’t shift into 4 wheel drive. Replaced the shift module with an after market module and when that didn’t work I replaced it with a Motorcraft module. That didn’t work either. Both relays have been replaced and I’ve ohmed out all of the wiring.Don’t know what to look for next.
Thanks