Can't use hard drive no matter what

The summary of my situation:

• 1 TB Nvme SSD (Windows)
• 1 TB WD Blue Internal HDD (Kubuntu)
• 8 TB WD Red Pro Internal HDD (not working)
• 1 TB WD Passport (Backup of Windows)

Windows is on my C: drive, and my 8 TB HDD was the D: drive. However, my external backup was also the D: drive, so when I plugged it in, Windows just stopped acknowledging the existence of my 8 TB HDD. I changed the letter of the backup to K: but still nothing. I also can't format the drive, and I can't initialize it. I uninstalled the HDD and unplugged, then replugged it in before restarting, and still got nowhere. I haven't been able to access the drive to format it in any capacity on Windows or Kubuntu. I've been able to verify it works though.