Mac OS Sequoia not recognizing USB Flash Drives: upgraded today and now all work can not continue because usb drives can not be used on my mac studio. Did all the troubleshooting it is not my drives. Tried 2 hubs and plugged thumb drives into another external and still do not mount....does not work.
Mac Studio, macOS 15.7
Many users have reported USB drives not mounting after the update.
First, open Disk Utility and check if the flash drive appears but isn’t mounted, if it does, try mounting it manually. If it’s missing entirely. Go to System Settings > Privacy & Security > Files and Folders to ensure apps or Finder have full access.
Also, in finder < Setting make sure to check these options as shown in the image below.
Delete all partitions and reformat the drive on a Windows PC. This works for me sometimes.
Mac OS Sequoia not recognizing USB Flash Drives October 2025
