Hi Dave
As someone who, now retired, but after a career in commercial software development and project management of software development projects. I know when software is not working. In MSFS ALTkey + n switches to the custom camera n. FSUIPC7.4.x does not seem to recognise the combination ALT+n. Instead all it sends to PF3 is n (n=0-9) which triggers the hotkey n. Making a flight impossible if you have custom cameras.
Regards