Big Sur - no longer recognizes hard drive

Readers may be able to provide more guidance if you provide the Make&Model of your drive.

Some drives as shipped rely on a Proprietary Software Driver, which may not be supported or loaded on the new version of MacOS, which has many more restrictions.

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When you use a proprietary Driver, the drive is only recognized when full MacOS is up and running with all drivers loaded. (i.e., NOT Safe Mode, NOT Recovery, NOT Installer/Utilities).

Our recommendation is to always COMPLETELY erase a new drive in Disk Utility, and NEVER install the proprietary Drivers.

If you Installed the Vendor's Utilities, and never erased the drive with Disk Utility when new, then the drive is likely controlled by the Vendor's drivers.

You can do any one of:

Update the vendor's drivers for Big Sur (easy, if available)

backup your data and ERASE the drive with Disk Utility

roll back to the previous MacOS version

I have the same problem. External volumes will not appear in Finder.

I've found a work-around, but it's far from ideal.

Can you check if you can see the volume in the disk utility app (DUA)?

If it's connected via USB, it should appear there. From the DUA, you can eject the external volumes as well, before you disconnect then USB-cable. If you don't eject them properly, Mac OS X will notify you that the volume was not removed properly, as in previous OS x versions.

see if Western Digital has updated drivers that will run correctly under Big Sur.

I HAVE THE SAME PROBLEM , should we downgrade to an old OS?