If it was working okay before, then it's probably a problem to do with fueling rather than anything else.
I'd stick a couple of petrol cans' worth of new petrol in the tank (put about 250ml of paraffin in there too) to boost up the petrol, though 3 months old should still be okay.
You could have a flooded engine, or conversely a fuel starvation issue (blocked fuel filter?).
You can take the plugs out and let the beast dry out a bit while you clean the plugs up.
You can test for fuel flow by disconnecting the fuel pipe at the injector rail and cranking the engine over (you might want the plugs back in for that..
) . You should get fuel being fed to the rail while the engine is cranking.
No fuel.. could be a blocked filter.
If all looks well, check that the injectors are pulsing when you crank the engine. You can bend the tangs of one of those glass bottomed bulbs outwards and stick them in the injector plug (connecting to the metal contacts). If it flashes when the engine cranks, then the injector is getting a signal and the problem is not the TDC sensor.
Check that the spark plugs are sparking. If you have an old plug, lay it on the block connected to an HT lead and see if it sparks when you crank the engine.
If you have fuel, injectors and sparks then the beast must start eventually (use "hot-start" technique - basically hold a half or even full throttle on .. if you think the beast is flooded). Otherwise, don't touch the gas at all. Just turn the beast on and crank it four or five seconds at a time.