External drive

Just to add to the already good advise

Allow USB and other accessories to connect to your MacOn Mac laptops with Apple silicon, you might need to approve new accessories before they can connect.

Copy and paste from the above link

" When you use a new or unknown USB accessory, Thunderbolt accessory, or SD card with your Mac laptop with Apple silicon, you get an alert that asks you to allow the accessory to connect. 

• If your Mac is locked, you need to unlock it before you can allow an accessory to connect.
• If your Mac has been locked for 3 or more days, you might need to unlock it to use a previously allowed accessory again.
• If you click Don't Allow in the alert, your Mac won't recognize the accessory or give it access to the data on your Mac. The next time you connect the accessory, you'll be asked to allow it again.
• Accessories can still charge your Mac (or themselves) even if you choose Don't Allow.

Finder menu > Settings > General tab, tick the box to show External Disks. Change the same setting on the Sidebar tab, if you like.

If those boxes are already checked, then open Applications > Utilities > Disk Utility, select View menu > Show all devices. Does it show up there, and if so, can you mount it (button in the top toolbar)?

More info: Disk Utility User Guide for Mac - Apple Support

If you have a Mac laptop computer with Apple Silicon (M-series, and not applicable to Mac desktops), accessories must be allowed to connect. Go to System Settings > Privacy & Security > Accessories, try changing it to Automatically allow when unlocked or Always allow.

If you have 3rd party ‘protection’ software installed, that may be the problem. For example, ESET has been reported to prevent external drives and memory cards from mounting. Such 3rd party system ‘helpers’, ‘cleaners’ and ‘protectors’ do more harm than good. In fact, such products are completely unnecessary for macOS and the only ‘good’ (if you want to call it that) they do is to put money in the developers’ pockets. For the user, they offer only harm…and if that is limited to harm to your bank account, then count yourself lucky.

There were a few prior posts on this forum from users who couldn’t access their external drive due to the drive manufacturer’s software that they used to encrypt the drive. Lacie/Seagate, Samsung, SanDisk, etc., all provide 'drive management' software on their drives and using such 3rd party software can cause issues when macOS is updated and the 3rd party software becomes incompatible. Not sure if that's the issue here, but FYI the best practice with a new external drive (SSD/HDD, not applicable to NAS drives) is to use Disk Utility to complete erase it, format it as GUID/APFS and apply encryption if desired.

If your drive is using a FireWire connection, it will not work anymore because starting with macOS 26 Tahoe, FireWire has been fully deprecated by Apple and is no longer supported.

FWIW, I have a bunch of Samsung T7 and T9 SSDs ranging from 1 TB to 4 TB and a pair of Crucial 8 TB SSDs, and they all work fine with my M4 Pro MacBook Pro running the current version of macOS.

Final note: if nothing at all is showing on your Desktop, go to System Settings > Desktop & Dock and make sure the box to Show Items On Desktop is checked.

The fact that your WD drive works normally on another Mac is a useful clue.

Since you have already formatted the drive and checked both Finder and Disk Utility, I would not  reformat it again just yet.

There is one other thing worth checking on the Mac where the drive works. 

Does that Mac have any WD or other third-party software installed that manages, secures, encrypts, backs up, or otherwise controls the drive? 

If so, let us know the name of the software and, if possible, its version. 

This could be an important difference between the two Macs.

On your new MacBook Pro, connect the WD drive directly and go to Apple menu >> System Settings >> General >> About >> System Report… >> USB. 

Check whether the WD drive appears there.

If it appears, open Disk Utility and select View >> Show All Devices. 

Check whether the physical WD drive and its volume are shown. 

If the volume appears but is not  mounted, select it and click Mount. If Disk Utility reports a problem, First Aid can then be considered.

If the WD drive does not appear under USB, try the other USB-C port and, if possible, a different compatible USB cable. 

If the drive has its own power supply, check that connection as well. 

The LED lighting up confirms that the drive is receiving power, but it does not necessarily mean that the Mac is communicating with it.

Your other external drive working on the same MacBook Pro is also a useful comparison. 

At this point, the two most useful things to establish are whether the WD drive appears under System Information >> USB and whether the other Mac has WD or other third-party software installed that manages the drive.

Apple's relevant instructions are here: Connect and use other storage devices with Mac and Disk Utility User Guide.

Why not?

What happens when you plug it in exactly?

Does it issue an error? If so, what does it say?

How are you trying to connect it to the Mac?

Are you using an adapter?

How is the drive formatted?

Where on the Mac are you lookig for the external drive once connected?

Please provide some details and context and someone here may be able to advise.

click here ➜ Writing an effective Apple Support Communities Question - Apple Community

when I connect it, the led light blinks once and stays steady. No error messages. I am plugging the drive directly into the laptop without any adapters. And I formatted the drive and looked in the finder and Utility apps.

I connected my 2nd external drive which has a copy of all my music and that connects fine with no issues. I also checked the I information on both drive and everything is the same. strange this is that I connect the drive which is not connecting into another Mac Pro laptop and the drive connects?

I did this already and it is still not connecting.

Thank You

You are welcome

Then, I would personally suggest following the advise from @ Phil0124

Based upon the limited Technical Details provided

Their advise would be invaluable

I tried all that you sent me and still does not connect.

Thank you for your help