Hi, NickHopwood!
Thanks for reaching out to Microsoft Community and posting your concerns regarding the Type Cover of your Surface Pro 4.
To initially troubleshoot the issue, kindly detach the Type Cover. Check if there are any debris that may inhibit connection and clean it when needed, then force shutdown the device and restart.
1.) Press and hold the power button until the screen turns off (about 10 seconds), then release the power button.
2.) Press and release the power button to turn your Surface back on. You should see the Surface logo.
If that doesn't work, use this two-button shutdown process to make sure your Surface turns off completely:
1. Press and hold the power button on your Surface until the screen turns off (about 30 seconds), then release it.
2. Press and hold the volume-up button and the power button at the same time until the screen turns off (about 15 seconds), then release both.
The screen may flash the Surface logo, but continue holding the buttons down for at least 15 seconds.
3. After you release the buttons, wait 10 seconds.
4. Press and release the power button to turn your Surface back on. You should see the Surface logo.
Then re-attach the Type Cover and check if it works. May we also know if both keys and touchpad are affected?
If the issue is still present, please go to the Surface UEFI.
1. Select Start> Settings > Update & security > Recovery.
2. Under Advanced startup, select Restart Now.
3. Under Choose an option, select Troubleshoot > Advanced Options > UEFI Firmware Settings, and then select Restart.
4. Verify if keyboard (arrow key) allows you to progress through the menus, or the touchpad allows control of the mouse arrow.
5. Go to Devicesas well and check Type Cover port, see if it is enabled or not. Make sure to enable.
6. Hit on Exit, then Restart.
Let us know how it goes.
Kind regards,
Janette_Z