Sorry I didn't explain very well... if you have PF3 running on a client using Wideclient you might be using the keyboard attached to that pc, in which case you would need to have the Wideclient window at the front with focus. If you're using the keyboard attached to your FS pc then yes, you need MSFS at the front.
If you get the same problem again I would suggest you save the wide client log plus the other logs you showed me earlier and report to the FSUIPC team... they should be able to help a lot more than I can with this particular situation