Lately, USB 3.0 thumb drives that I've used for years will not load on my iMac 27" 5K, late 2015. The exact same drive will pop up immediately when used on my MacBook Pro 13" running Big Sur 11.6.8. The drives will not even show up in Disk Utility on the iMac. Is this a known software bug??
Are you connecting the USB stick directly to the Mac?
Try booting into Safe Mode to see if you have the same problem just in case you have some third party software installed that is interfering with the normal operation of macOS.
What file system is on the USB stick?
Within Disk Utility you may need to click "View" and select "Show All Devices" in order to see the physical drive on the left pane of Disk Utility. If you don't see the physical drive on the left pane after doing this, then there must be some sort of compatibility issue. Disconnect all other unnecessary external devices in case one of them is causing a problem. macOS Monterey has had a lot of reported compatibility issues with each update patch so it would not surprise me. The quality of USB sticks is also very poor and I have seen compatibility issues and reliability issues even if the USB stick works with many other systems.
Are you connecting the USB stick directly to the Mac?
Try booting into Safe Mode to see if you have the same problem just in case you have some third party software installed that is interfering with the normal operation of macOS.
What file system is on the USB stick?
Within Disk Utility you may need to click "View" and select "Show All Devices" in order to see the physical drive on the left pane of Disk Utility. If you don't see the physical drive on the left pane after doing this, then there must be some sort of compatibility issue. Disconnect all other unnecessary external devices in case one of them is causing a problem. macOS Monterey has had a lot of reported compatibility issues with each update patch so it would not surprise me. The quality of USB sticks is also very poor and I have seen compatibility issues and reliability issues even if the USB stick works with many other systems.
Disconnect anything connected to the USB ports on your iMac. Reboot, and try your USB stick again. If that does not resolve the. mounting issue, then boot your iMac into Safe Boot mode and see if the USB stick will mount. If it does, and upon a normal reboot, it also connects, then problem solved. On the otherhand, if it mounts in Safe Boot mode, but fails mounting after a normal reboot, then you likely have some third-party software interfering with it.
Thank you for the detailed response. I am connecting the USB stick directly to the Mac. I will try in safe mode. The file system is Fat32, I believe. Whatever the stick comes with as default.
Even when clicking "Show all devices" in Disk Utility, it does not show.
I will also try Safe Mode!
Just to add, you might want to try a different port if you haven't already.
Also, try resetting the SMC.
USB thumb drive will not work on iMac with Monterey 12.5
