Ports Not Working after Tahoe

Confirming multiple steps you mention having taken, because I also have a 16” M1 MBP on 26.3, and external SSDs and camera cards (SD in the built-in slot, CFeB in a USB-C reader) all mount normally. Same is true on my 16” M4 MBP.

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?

If you have a Mac laptop computer (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.

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 theissue 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.

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 OnDesktop is checked.

As a Last Resort

Attach the problematic drives to another Apple Computer

Do they work ?

Attach the problematic drives to another MS Windows computer

Do they work ?

This would help determine if the problem is with " Ports Not Working after Tahoe " or if the drives themselves that are the real issue

Is this " MacBook Pro 16″, macOS 26.3 " an Apple Silicon Computer ( M1.M2.M3.M4 ) ??

Allow USB and other accessories to connect to your Mac

You say, those setting have already been set Correctly ?

Check again

If Yes then the usual questions to be asked

1 - How, exactly, are the drives Physically attached to the Ports

2 - In what, exact, format are the drives. APFS / GUID Partition Map, HFS Journaled / GUID Partition Map. Fat 32, exFat,

NTFS , ext4 formats ?

For drive formatted in a Windows NTFS format you can Read from the Drive but can not Write to the drive without special Third Party Software installed

Drives attached through a Powered or USB Powered HUB have be problematic

All the above is important in attempting to assist with this issue

Get yourself a cheap USB-A to USB-C passthrough adapter

This baby has worked fine since about macOS 11 Big Sur and every newer version of macOS including Tahoe 26.3

Circhenn wrote:

Thanks for that reply. My Macbook is a 16" with an M1 processor.

I have taken action as you suggested but the settings were already as you suggested.

If we may make a friend suggested not related to the issue at hand

Go to your User Profile on these Forums

Look for " Preferences "

Scroll down to " Other Preferences "

Change that setting to " OLDEST "

This way, you will seen the replies in Chronicle Order by Date with Oldest at the bottom

That should help to Not Reply to Yourself

Circhenn wrote:

Thank you, I have ordered one of these 🤞

Let us hope this will work

But You wrote " Cannot mount from Disk Utility "

So the drives do appear in Disk Utilities and can not mount ?

This is starting to look like the drives ( themselves ) are the problem

Whether the USB-A to USB-C passthrough adapter will or will not solve this

It remains to be seen