Earlier today I opened up my T510 for maintenance. In doing so, I removed the keyboard. After putting everything back together, the TrackPoint/TrackPad, mouse and all mouse buttons did not work.
I had not removed the TrackPad. I then removed the keyboard several times to make sure that it was properly installed and connected and to check for physical damage - there was none.
The keyboard is working though.
This could be a result of a cable latch being incorrected secured.
This workaround was contributed by a member of the community:
The TrackPad is connected to the motherboard through a cable labeled as a speaker wire in the Hardware Maintenance Manual, which is visible after removing the keyboard bezel and TrackPad from the system.
There will be a small latch to hold this cable in place and connect it to the motherboard.
Check that the secured and unsecured states for this latch are in the right positions.