1st step does the fuel pump rpime or run continuously when you turn the key 1 click.
next step is to double check the timing, one thing that can sometimes catych you out is the cam pulleys have a punch mark on both sides as its also used for the intermediate shaft, if you put it on back to front the marks dont line up!
Have you visually confirmed the cam lobes on #1 are pointing up and way from each other at TDC, like this |\ /|
Also check the rotor arm, it will spin freely if the belt is removed which catches some people out the 1st time, me included
Make sure the rotor is pointing at the notch in the edge of the dizzy lip, and fit the #1 spark lead to where its pointing at. Firing order from there is 1 3 4 2 clockwise. Then just verify the bottom end is at TDC by shining a torch down sparky hole #1.
Appologies if you know all this but its always worth mentioning!
If all that checks out, has the blue temp sender been replaced recently, a faulty one will prevent a digi mk2 from starting. Get a new one from VW if there is any doubt, only £13ish
