Hi John,
I've taken a look at the log you provided and can see that you correctly tuned to the Tower on 120.7 (per handoff) but then the radio was retuned to 123.8 before you used Hotkey #1 so PF3 ignored the keypress. It accepted Hotkey #2 a little while later, as by then you had retuned to 120.7
I believe that this is an interaction from one of the MSFS Assist options, as Dave previously suggested - the MSFS ATC frequency for KTTN Approach is 123.8, but this was altered by PF3 to avoid a clash with KTTN Departure.
Airport KTTN :N40:16:36.0861 W074:48:48.4990 184.74ft
ILS: ITTN 111.30 Hdg: 58.5 , Flags: GS BC Slope: 3.00, "ILS RW06"
in file: Official\Steam\fs-base-nav\scenery\0302\NAX28170.bgl
COM: Type=8 (APPROACH), Freq=123.800, Name="PHILADELPHIA"
COM: Type=13 (ASOS), Freq=126.775, Name="KTTN"
COM: Type=1 (ATIS), Freq=126.775, Name="KTTN"
COM: Type=7 (CLEARANCE), Freq=121.900, Name="TRENTON"
COM: Type=9 (DEPARTURE), Freq=123.800, Name="PHILADELPHIA"
COM: Type=5 (GROUND), Freq=121.900, Name="TRENTON"
COM: Type=6 (TOWER), Freq=120.700, Name="TRENTON"
COM: Type=3 (UNICOM), Freq=122.950, Name="TRENTON MERCER"
FSM A/P KTTN, lat=40.276695, long=-74.813469, alt=184.74
Cheers,
Martin