You need to physically check the requirements for starting are being delivered into the cylinder.

An engine needs a good supply of fresh fuel to be delivered in the correct quantity into the cylinder which then needs to be compressed and then fired by a good strong spark at the right time.

Fuel, compression, timing and spark. If all those are present and the engine cranks quickly enough it will start. As it is not starting one or more of those things is absent or faulty.

If the plug is getting wet with fuel after cranking it could be getting too much (flooding) or it could indicate absent or insufficient spark. It is partly a process of elimination and partly the testing of components and process and partly being a detective.