Jill, sorry you are having problems with the fridge. I double checked and we don't have an additional valve for the propane on our fridge. Here's what I would do if I were you:
1) Double check and make sure the propane is working by lighting in the stove and making sure you have a good blue flame. I think you can also see/hear the burner at the back of the stove and see whether or not it is lighting.
2) Make sure you have adequate 12 volt power -- the fridge requires 12volts to operate, even on propane. If the furnace is running, I am pretty sure you have 12 volts, but just to be sure.
3) My vague recollection is that there is a reset procedure for the fridge after it alarms. I think you have to turn it off, wait a minute or so and then turn it on again. This is the RV Dr's take on the old "Reboot your computer trick.".
4) Make sure door is closing properly -- all shelves properly secured, etc. It will alarm if the door is open for too long.
5) RBryan4 and Carl in Florida had problems with the alarm sounding even though nothing was wrong. the ultimate solution was a control board replacement, but they kept temporary sanity by unplugging the light. You can find out more in this thread
6) There is a fuse associated with the fridge. If you are getting the alarm I assume it isn't blown, but it wouldn't hurt to check it out.
I hope you find a fix!