Walk-Behind Mowers

I purchased a PR550N21SH in august. It took 3 pulls to start the first time, 6 pulls the second time, and 10 the third time. The fourth time it would not start at all. I had surgery and could not use it until November and it would not start. Plenty of gas and oil and the spark plug appears good. The serial number is 17 0612 51 8557 and the MFG ID is 96132010101. Any help would be appreciated.

joe