First of all, check if the display is lit when the device is plugged in.
If your device doesn’t light up when connected, try using a different USB cable or USB port, and make sure that you are connecting your Trezor with the cable directly. Please don’t use a USB hub or adapter. Also, if possible, try connecting your Trezor to another computer. Some USB cables do not allow data transfer, so even though your device has power it may not be recognized by your computer.
If it’s lit, find out if the device is recognized by device manager.
If it’s not recognized, perform the troubleshooting steps described above.
If it’s recognized by the device manager, there might be a problem with the drivers
Try (re)installing the newest Trezor Bridge version from this source (once installed, please proceed by clearing your browser’s cache). After successful installation, you should see a process named “trezord” running in your activity/system/task monitor.
If none of the above helped, please contact our customer support: customer support contact form.