Thanks, I tried removing the battery, and all the things other URC mentions here but no luck:

https://urcfaq.knowledgeowl.com/help/cant-connect-or-download-mx-780-mx-790-mx-890-and-mx-990

I also unsuccessfully tried it on two more PCs running W10 including an older one that only has USB 2 ports since URC mentioned that might be a solution too. I will try it at my local URC dealer today as I know he sells 990s.

I also tried the factory reset mentioned here on the forum where you hold on and mute while inserting the battery. This didn't seem to do anything after rebooting as it just goes back to what I assume is the default screen with a number of device icons that don't do anything, so perhaps the remote is already reset. In any case it still doesn't show up in device manager as a device.