Almost 10k on/off cycles + 100k hours lol

Hi alll.....last night I erased my iMac (Sequoia). After restart, I connected my WD external hard drive and began moving a few folders over. Worked great. The drive also worked perfectly fine on my Macbook Pro (Catalina). I used Migration Assistant to transfer some files to the iMac from the MBP. As that was finishing, iMac froze on black startup screen but wouldn't progress from there. I realized I had left the ext HD plugged in, and knowing from the past this causes issues, I unplugged it. It unfroze and finished restarting just fine. Now, the ext HD does not show up on either of my Mac's desktops, but does show up in Disk Utility, although it will not mount. Format is ExFat. I plugged it into a Windows PC and then back to my mac....no change. It does show up just fine on the PC and I can access the files successfully. Anyone have any ideas or thoughts on what changed?? I appreciate all of the help in advance!

Also wanted to add that when I click on First Aid, it immediately fails.