Ah okay that error makes more sense.
Just confirming that the KrakenSDR was powered during the tests on Windows?
If it was definitely powered, please email thekraken@krakenrf.com. It does sound like something failed on the board.
Yes, I had the KrakenSDR powered up with the official pi 4 Canakit AC adapter rated for 3.5A when I tried connecting it to my two Windows PCs. I will contact you via email. Thanks for your troubleshooting advice.