Did you take the engine to pieces, I can't remember? If you did and reset the valve timing, maybe it is out. When I did mine, even with the tappets backed right off, the cam moved after it had been set because of the pressure from the valve springs. You have to block it once it is set
However, if you haven't touched that and it ran before, it can't be valve timing. Maybe first principles - rocker covers off, see which cyl has both valves closed (ie firing) and see which lead the rotor arm is pointing to and go from there. I do a full cycle to check each firing stroke and corresponding lead
With the rockers off you can also see if any valves are stuck .....
If that's OK and there is a spark, back to petrol and compressions