If you're experiencing issues with USB on your Mac after installing macOS Sequoia, you're not alone, with some users reporting drive connectivity issues.
macOS Sequoia with iPhone Mirroring
Following the release of major operating system updates, there are often small issues that crop up that weren't picked up during the beta-testing process. As expected, this has happened to macOS 15 Sequoia, which was released on September 16.
There are a few reports on Reddit and on Apple's support forum claiming that some upgraders to macOS Sequoia are having USB port trouble. Drives and chargers plugged into the USB-C ports of a MacBook aren't being detected, or take a long time to become usable, one Reddit post claims. There are other similar reports on Reddit as well.
Others in the Apple support community discovered that their USB flash drives aren't being recognized. They simply do not appear in Disk Utility at all, meaning they aren't even mountable in the current state.
It appears that the issue isn't limited to a specific model, nor to a chip, with M1, M2, and M3 chips seemingly affected, as are the MacBook Air and iMac.
It is unknown if Apple is aware of the issue. Online reports don't mention any communications with Apple's support teams.
We can't reproduce the problem across any combination of hardware. To date, the issue doesn't appear to be widespread, as there would be much more conversation about the issue if it were.
AppleInsider suggests that affected users should contact Apple Support so that the problem can be acknowledged and a potential software fix worked on for a future update. Apple does not respond or catalog social media reports of problems.