Linux users, please verify your udev permissions. This applies to the Nano, HW1, and Nano S.
The section below applies to Ledger Nano (not Nano S) and HW1 only:
If unplugging and plugging the hardware wallet doesn't correct the problem, then it means your firmware update was not successfull. To fix the issue, you need to reflash the Nano again, but using a different method: