Device not recognized in bootloader mode
From Trezor Wiki
This article is a workaround solution for users who are unable to access the bootloader mode and cannot get to the firmware update screen when using their Trezor device with a Windows 8 or 10 computer.
Please follow the instructions below:
1. Connect your Trezor device and download this file and open it (admin mode might be required).
2. Confirm both dialogue windows.