APRS Mute on FTM-100 is a real "GOTCHA!!" on the Yaesu FTM-100 radio. With APRS Mute set to On, the radio will hear NOTHING. The speaker is muted for Band A and Band B even if you are working APRS on the other.

If you are having trouble receiving a signal and Tone Mode is not set to TSql (a very common accident), check this option on the Settings | Radio Menu Settings | APRS | Aprs Mute (bottom of second column of options: just above message Group) .

Once set to Off, Save your settings file before exiting. Then write the file to the radio to make the change there.