So the check light means the flame went out and this could be a number of things. When you troubleshoot these it is a process of elimination.
Right off the bat I would do a few things, get an air nozzle and blow out the burner tube really good, the burner tube sits below the electrode or what sparks, sometimes debris can get inside and cause issues with it lighting off or with the flame going out. Make sure it is clear and clean.
Make sure the electrode which sits above the burner tube is about 3/16" over the burn tube. I might also remove the gas orifice and soak it in alcohol.
After that it gets a bit more complex, my guess would be the thermocouple and that is the first part I would replace. Make sure the DC voltage going into the terminal block is also around 12 volts, low voltage can cause these to shut down.
To help you more on this click HERE and see page 12 for check light ON and then you can look in the manual at each component that is metioned.
Hope this points you in the right direction, if you have more questions or concerns please feel free to contact me.
IF you are satisfied with my efforts please feel free to select a STAR rating on the page....
Also want to mention the LP it really should be checked yearly with a manometer to see what the operating pressure is, would be hard for you to check without that tool, so you may have to skip that part. In the shop it is a 15-30 min check.... Robert