I'm not sure why the buttons aren't working if you are able to see the In-Game display in MSFS - perhaps you could try the following for me:
1) Check that the options in PF3 are set like this:
2024-08-21 PF3 Options.png (59.13 KiB) Viewed 25610 times
[PF3WebDisplay]
WebPort=
PF3Port=
PF3Host=
ATCRadio=Yes
RemoteText=Yes
3) Start MSFS and set-up your flight, then start PF3 - it should start Web Display automatically using the default settings.
4) Try connecting to Web Display from a browser on the PC on which you're running MSFS & PF3 (http://localhost:7339) - you should see something like this:
2024-08-21 Chrome.png (69.41 KiB) Viewed 25610 times
If this is working correctly then please proceed to step 5.
Otherwise, we first need to resolve this issue; please skip to step 6)
5) Web Display seems to be working, so now please try opening it within MSFS (preferably outside VR).
If you hide the default commands and then click the button to the right of 'Radar Freqs' then you should see something like this:
2024-08-21 In-Game.png (404.27 KiB) Viewed 25610 times
6) If either the browser or In-Game display aren't working correctly, please disconnect PF3 from MSFS and exit it to close the log files cleanly.
Then upload the file PF3WebDisplay.log that can be found in the folder where Web Display is installed (default is PF3_WEB_Display).
Also, if you're having problems with the browser, please let me know which one you are using - Chrome, Firefox or Edge should all be okay.
Please let me know how you get on. These screen shots were taken from my own FS system this morning, and all is working as expected.
Martin