OP - first determine what is the problem. Start by having assistant crank engine normally ( clutch/brake fully depressed, PTO switch off, Choke off, throttle 1/2) while youy spray several shots or rattlecan carb cleaner directly into open carb throat (air cleaner removed) - if engine "pops" or tries to run, problem is fuel delivery. If not, problem is ignition or mechanical.
Ignition - Purchase ignition spark tester from briggs shop so that you can chk for spark with plug IN ENGINE and UNDER COMPRESSION. Will msave you a ton of diagnosis time and inexpensive. If ignition OK, remove flywheel and verify flywheel key not partially or fully sheared. Consult engine service manual for procedure (a must).
If no ignition at all, then time to trace OPR's (CL/BR sw, Seat SW, etc.) for proper function. Crank but no start is most often associated with defecvtive seat switches and on most models, you cannot simply "jump" them out of the circuit.

Mechanical - pull valve covers, chk for loose rockers/rods/etc. cranke engine over by hand and observe lifter movements for consistency.
fuel delivery - remove fuel hose at carb - crank engine - catch fuel - should be a good amount/flow. If not, trace back for problem, repair/replace including fuel pump, fuel filter, flexible fuel lines back to tank. Also chk vacuum relief at fuel tank cap. Make sure only OEM fuel filter for engine make/model is installed - no aftermarket.
If fuel flow OK at carb, pull/disasm carb. soak in carb cleaner overnite. Using small dia stiff brass wire and MAGNIFYING GLASS, probe ALL component orifices and blow out same with clean compressed air. reasm carb using new rebuild kit and all new gaskets/seats. Retest on engine.
good luck.