It's a fact of life with this PC -- I have a fair number of USB sticks/drives, and sometimes they won't show up in File Explorer when they're plugged in. The 1st thing to check is Control Panel -> Admin Tools -> Computer Management -> Disk Management, and see if you need to assign a drive letter -- Windows tries to remember the last drive letter used for that device, and sometimes a conflict will result in no letter assigned. IF it doesn't show up in Disk Management, often plugging the stick/drive into another USB port works. If that doesn't, restarting Windows normally does. However, I just had a USB stick where none of that would work. It showed up with the Task Bar USB icon, but that was it. In that case check the device with another PC/laptop -- it might have died -- and plugged into my wife's PC this USB stick was fine. When you've reached this point there's a tool that can help, USBOblivian, but it's a rather blunt tool, deleting all the data Windows stores about the USB devices you've used. cherubicsoft[.]com/en/projects/usboblivion/
I wanted to take a more targeted approach... with the USB stick plugged in I opened Device Mgr. [it's in Control Panel] & selected view devices by connection. Expanding the trees as necessary, I found the USB stick, right clicking & selecting properties. Going to the Details tab, you can find all sorts of info depending on what you select in the dropdown menu -- I copied several IDs to a new doc in Notepad, then searched for them under Hotkey Local Machine\ System in Regedit [right click the Start Button, click Run, type regedit & press Enter]. In Regedit you can right click any key and export [save] it, which is probably a good idea before you start deleting stuff -- if there's a problem, double clicking the saved .reg file will add it back. In this case I had to delete the values in the keys I found since the keys themselves were protected, but it worked -- I did have to assign a drive letter in Disk Management, but otherwise the USB stick is working normally again.