Thank you for the log, I can see what the issue is:
18:04:11 812 PF3 Web Display: Server Release 2.3.1 - Template Release 2.3.1
18:04:11 815 PF3WebDisplay.ini file not found, using default values
18:04:11 818 PF3 address 127.0.0.1, PF3 Display port 1010, WebSocket port 7339
18:04:11 836 Starting PF3 Display interface ...
18:04:11 850 Connected to PF3 Display ...
As the .ini file could not be found Web Display works like PF3 Displayer - it does not enable frequency changes.
You say that this was working previously, so this suggests to me that the .ini file has somehow been deleted.
If you create a file called PF3WebDisplay.ini containing the following then everything should return to normal for you:
[PF3WebDisplay]
ATCRadio=COM1
This, and other options, are documented in the Web Display PDF, which you should find in the Web Display folder.
I hope that this helps,
Martin