Hi RAnna1,
Thank you for reaching Microsoft Community.
Does the grey spots appears like these?
If yes, these are phantom/ghost touches on the screen where the screen acts as if it is pressed on those area making you unable to navigate using the mouse or keyboard. These spots are usually difficult to see on the UEFI screen since the UEFI screen has a white background but doing the USB Reset should have fixed the issue if it is only caused by a software on the device. Since the phantom touches persist even after the USB Reset, this is likely a hardware issue already and a replacement will be the next option. See this page for details Get service for your out of warranty or damaged Surface (microsoft.com) or contact support for further assistance.
If I may suggest, you may also disable the touchscreen drivers of the device for you to continue using the device through the keyboard or mouse since this will disable the touchscreen functionality of the device. To do this, follow these steps below:
Open Device Manager, expand Human Interface devices
Right-click on HID compliant touchscreen and select Disable device
Right-click on Intel Precise Touch and select Disable device