SOunds like the burner and or ignitor may need cleaning. There could be debris obstructing the flow of gas in the burner at the proper spot for ignition or even blocking the path for the high voltage to find ground. If after cleaning you still do not get spark then the control board would be the next place to look.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7