You can try to disable and enable it in device manager and checking for driver updates. 

Test it by adding an external usb mouse. Also Check the mouse settings in Control Panel. The pointer settings might have changed. Hide the pointer might be selected.

Simple 

Reboot to BIOS (F2) 

or Reboot to ePSA (F12 > Diagnostics) 

If same issue there as well, time to get in to hardware part. 

Reseat Touchpad cable you can use service manual found at support.dell.com

If no go

get a new touchpad (assuming bios is updated)