If your Western Digital hard drive doesn't work after a macOS update, you should first ensure it's well-connected, then check if it's detected on Mac and if your WD software is having issues.
I know that the hard drive worked fine before the update, so you may assume the cable or port has no issue. But you're still recommended to check the connections. Try these:
- Attach the hard drive to a different USB port.
- Use another USB cable if available.
- Try a powered USB hub.
- Ensure the drive is firmly connected.
- Reboot your Mac.
- Plug your WD external hard drive into a Windows PC
After that, you need to check if your WD hard drive is detected on Disk Utility. If it's not, download iBoysoft Data Recovery for Mac to see if it sees the drive.
If your drive appears on the app, recover your data and reformat the drive will make it work again.
If your WD hard drive can't be recognized on Mac despite having a good connection, continue working on these:
1. Use WD Discovery for Mac
Have you installed WD Discovery for Mac to help you manage your hard drive? If you haven't, install it to see whether it mounts your hard drive. If you have, check if it needs to be updated to work with the updated OS. Besides, test if it helps to turn off UAS in WD Discovery by selecting the Storage tab, clicking the gear icon next to your drive, and choosing the UAS option.
2. Unlock the drive in WD Security
If your WD hard drive is password-protected, macOS can't read its partition information and mount it. You need to install WD security to unlock it.
3. Diagnose your drive with WD Drive Utilities
There could be disk errors that are preventing Mac from recognizing your hard drive. You can use the app called WD Drive Utilities to diagnose and fix these issues. If it finds errors it can't repair, you can download iBoysoft Data Recovery for Mac to recover your data and then reformat the drive.