I agree it is not getting gas. If it runs on a prime as you say, it is getting spark compress ion etc.
If you put the engine away with gas in the carb it is probably " gunked up" and a cleaning is in order. always run the engine dry at the end of the season.
do not run it on last years gas. Gas has a shelf life of about 3 months max
Assuming you have a Briggs and Stratton engine, if you go to their website you can download their manual
don't put a lot of gas in the tank because you will probably remove and replace the tank a few times in this process
for my 12 hp if reads like this
1 gently close both the idle and high speed needle valves... clockwise DO NOT OVER TIGHTEN
The idle valve is on the top and the high speed is on the bottom under the bowl
2 open the idle screw one turn counter counter clockwise and the high speed 1 1/2 turns counter clockwise. these are the initial settings to get the engine running
3 start the engine on run and then move the throttle to idle. If it won't run past the prime you need to clean the carb. Some times a little carb cleaner spray right into the gas will clean out the gunk.
After you get the gas flowing you can tweak the carb settings for a smooth idle and variable speed settings on the throttle