I see that your Mac can't recognize your Seagate external hard drive, and you've done some troubleshooting, including:
- Try different cords and outlets
- Check whether the drive appears in Disk Utility
- Test if a Windows PC can recognize the drive
But you haven't checked whether the drive is detected in System Information. Sometimes, an insufficiently charged drive won't appear in Disk Utility or the desktop, but it still shows up in System Information. Go to the Apple menu > About This Mac > System Report, and look for hardware information about your hard drive.
If System Information detects your external hard drive, you need to supply the drive with enough power. You can do that by switching to a better cable or ensuring the drive is charged by avoiding adaptors or using a different adaptor.
If System Information doesn't detect it, try:
- Connect the unrecognized external hard drive to another USB port on your Mac and ensure it's firmly connected.
- Restart your Mac.
- Use the drive on a different macOS version if possible. (Did you update your Mac recently? A new update may render issues with external hard drives.)
The goal here is to get your Mac to recognize your external hard drive. Since you managed to mount the drive by trying different cords and outlets, I'm leaning toward believing Mac can detect it after some attempts.
If Mac recognizes your Seagate external hard drive:
You mentioned that First Aid failed to repair the drive, so it likely has some corrupted files or file system issues. The easiest way to fix corruption like such is by reformatting the drive and assigning it a new, clean file system.
However, reformatting will erase all the data on your drive; thus, you must recover data from the corrupted drive first. The best corrupted hard drive recovery software is iBoysoft Data Recovery for Mac, and you can free download and install it here.
Then after the data is secured, you can reformat the external hard drive on Mac.
If Mac doesn't recognize your Seagate external hard drive:
If the drive simply can't be recognized on Mac, you should switch to your Windows laptop since it successfully mounted your hard drive.