Aidan,
Good to hear that you solved the issue but, for future issues you might like to try this...
https://www.uwe-sieber.de/misc_tools_e.html#arbiter
It won't sort issues with faulty cables or usb hubs but, sometimes Windows associates a Com Port with a particular application & won't let it go...
This application allows you to clear Com Ports... I use it when switching between my Meade & Celestron mounts as sometimes, Win 10 is reluctant to reassign a port to the mount/handset I want to update..
Cheers