Teensy 4.1 has a special feature to completely wipe its memory and restore a known-good LED blink program, the same as it had when it was brand new. We call it the "15 second restore", because you press and hold the pushbutton on Teensy for 15 seconds.
The button press actually needs to be more than 13 seconds and less than 17 seconds. You'll see a quick blink on the red LED when you're at the 13 second point. Release the button within the next 4 seconds. If you hold longer, it won't do the restore. When the restore starts, you'll see the red LED turn on solid and bright. The actual wipe and restore takes well over 1 minute (far longer than my attention span for any tech stuff). Know that it takes a long time and just patiently let it finish. When complete, your Teensy will reboot and you should see the orange LED blink slowly. That's your confirmation the erase worked and the memory was restored to the LED blink program it had when brand new.
Your PC will NOT see a serial port. It will be a HID device. On Windows Device Manager, sadly all HID devices look the same unless you do into the advanced properties and look at the ID numbers. Simplest way to confirm is to look at "Human Interface Devices" before the 15 sec restore and note how many you have. When the restore completes and the orange LED blinks, you should see 1 more.
Not sure if this will really solve the Windows driver issue you're having, but at least it'll give you a way to get back to the original HID device state Teensy 4.1 has when it's brand new and not yet programmed with any code that turns it into USB serial.
