Ground check is a good start, find it, clean it and shmear w/ anti-corrosive electric grease. Should also work that into your Spring prep treatment as routine maintenance for dependability. Camping is much more relaxing when you aren't spending your time fixing wonky comfort gizmos, that's what homes are for! May also have been air in the lines. Had the tank been changed lately or sitting a long time with them off? As previously mentioned; I've also had to wait several minutes for it to purge enough, then try again after they timed out once or twice.
Also, read into the tank flow safety shut-offs required within the last 20 years or so. It's good info to keep in the back of your mind. DW used to turn off the propane tank on our home grill before turning the burners off thinking it would purge the lines for safety, which it did. Trouble was when we'd try to start it days later; there was no back pressure in the lines, which it sensed as a leak and stopped the flow. After going on for too long, and reading up, we closed the valves, cracked the tank open for a moment, then opened slowly to re-pressurize the lines, which resets the safety valve and have had no problems since.Beats cranking on the tank bleeder valve every time