Hi Melissa Ingaruca,
Thank you for reaching Microsoft Community.
Just to confirm, this is the built-in SD card reader at the side of the Surface Book 2 keyboard/base, right?
On the Device Manager, please try to double-click on the APP server driver that is getting a question mark and share to us the error message it shows.
May I know what the make and model of the SD card that you are using?
Have you tried connecting this SD card to other devices to check if it is still working?
How about the other ports on the base of the Surface like the USB 3.0 port, do they still work?
Kindly try to open Disk Management. Press Windows key + X then select Disk Management. Once you have the Disk Management windows open, see if the SD card shows up on the available Volumes of the device. If it shows up, try to assign a new drive letter to the SD card. Select the and right-click the SD card then select Change Drive Letter and Paths. On the next window, select a new letter to be assigned for the SD card then click OK or Next. Close the Disk Management window then check on the File Explorer again if the SD card now shows up with the new letter assigned. If still not, restart the Surface to make sure changes and applied and check again in File Explorer.
Let me know how it goes and we may recommend other troubleshooting steps once we have received your responses to the questions above.
Kind regards,
Marrion