I have similar Problem with FSUIPC6 and P3Dv5.
I have 5 devices, but one of them is always not recognized by FSUIPC, I think this is the one with the highest ID.
I tried averything in the last couple of weeks, but I can't get it to work.
The last thing I tried was these steps you mentioned earlier:
1. Replace the complete [JoyNames] section in your FSUIPC4.INI file with just this:
So far you haven't made many assignments to any devices, but be prepared to make them again as the numbers may change (probably will), and now you'll see letters instead.
2. Now use the Windows Device Manager or Settings and remove all those devices. If the option to remove their drivers too, agree and let it happen. You may need to repeat this several times for the multiple entries looking the same.
3. Unplug all those USB devices.
4. Reboot the PC.
5. Start the sim, then when it is all ready, plug the devices back in, one at a time, leaving the Simple Solutions ones till last, and checking access each time in FSUIPC.
If there's still a problem, please supply those three files again.
The more drastic solution is Registry Editing, which it may come to. But let's see.
After that, all devices was recognized by FSUIPC, but after the windows reboot, one is missing again.
They are all listed in the FSUIPS.ini but one is not warking when I try to calibrate it in FSUIPC.
Here are the 3 Files you need, in a .zip
Hope for some help,