Here's a SUPER old documentation from SeaGate. Like Windows XP/7 old, but some settings may still apply on Win 10/11 in different settings menus.

Seems like a signing issue of some sort. Keep digging into "access denied external HD error".

There were some other "download this to fix files" tools on a quick Google. I would NOT, absolutely NOT trust or use them.

I would only trust manufacturer docs, specifically SeaGate, or similar (WesterDigital, Samsung, etc). Or Window docs.

As for the scan, it's been started so not much you can do. Give it more time. If it doesn't respond in 4-6hr I'd call it stuck and a failed attempt. No more scans IMO.

If unable to solve in a non-invasive solution manner, Brandon Computers appears to do Data Recovery. Also TecFix and TrueData in Winnipeg. The less you tamper, the higher their success rates. FWIW, I'll disassemble computers without hesitation, but I won't touch data recovery. Delicate finicky beast.

Good luck man!