I've got a bit of a mystery here. I have a Latitude E7440 that has an issue with the mousepad/buttons. The left click button works just fine, but that is it.

Right click does not work (be default)

The upper mouse buttons do not work

The touchpad works normally for moving the cursor around but does not register tapping.

The mouse "nub" located in the middle of the keyboard does not work. 

Here is the weird part. If I go into the touchpad settings and change the Right Mouse Button (RMB) so that it performs a left click then it works just fine, and Vice Versa with the Left Mouse Button (LMB). If I have the LMB perform a right click then it does nothing. Assigning other functionality to the mouse buttons (doubleclick for instance) works just fine. The only functionality that doesn't work is the right click. External mice that I have plugged into the computer have full functionality. 

Things I have done to try and fix the issue:

1. Reinstalled the dell touchpad driver.

2. Reinstalled the windows OS. 

OS:

Windows 10 Enterprise version 1803 (latest version I can go to at them moment)

Does anyone have any suggestions?