Electrum 3.3.4
Updated to latest KeepKey firmware 2 days ago
The cable works fine as the Keepkey will work with the Chrome Keepkey plug in.
So, it seems like an Electrum issue.
I haven't used my KeepKey in a while, so I wasn't aware of this issue. I just tried mine with the newest version of Electrum, and experienced the same thing.
The dialog box gives instructions to remove the device from the device list in Windows, and then reattach it to reinstall the drivers. I tried and it's still doing the same thing. I have not had a chance to install an older version of Electrum on a windows 10 machine to see if the new version is the issue. I might have a chance later this weekend if no body beats me to it.