You can easily remedy this resetting the I/O.
1. With your Digidesign Interface plugged in, power on the computer.
2. Launch Pro Tools
3. Click on Setup at the top of the Pro Tools window.
4. From the setup menu choose I/O.
5. To the left of the grid in the I/O setup window click on each path and then choose delete.
6. Choose delete on the error message that pops up.
7. Now that you have deleted all of the paths click “Default” and they will all return.
7. Repeat steps 5 & 6 until both the Inputs and Outputs have been reset.