Hi Dave,
Very strange! You have checked the 3 issues I would expect to cause problems. When you say the file name is correct, I take it 'file extensions' are normally visible on your PC? We have seen instances where people, not seeing the .pgp file extension have added it, in effect renaming the file pilotaware.pgp[.pgp].
Duh!!!
Just realised one fundamentally basic thing I have overlooked.
USB updates only work on previous software starting from 20160820. If your existing software is older than that, it doesn't contain the necessary USB stick reader. Might this be the case? If not, I am at a loss to know what is going on here. Lee might have some ideas.
Can you retry updating via Ethernet. Remove all the dongles, connect the Ethernet to your router then power up PAW and leave it for at least 20 minutes. Power down and disconnect, then replace dongles, reboot and connect to 192.168.1.1 and try the 'Check for Updates' again. Let me know how you get on.
Regards
Peter
Edit: Lee was obviously thinking the same thing and just beat me to the post. Embarrassed I missed that possibility - a schoolboy error on my part, Sorry !!