I am not sure if I understand you right, did it work on shore power? If so, did you recently change out or refill your propane tank?
The furnace works off of 12 volts reguardless of shore power. If it did work on shore power and not battery, your battery might be too weak. Check your voltage with shore power off.
If you changed tanks, you could have air in line. Purge it by lighting your stove for 3-5 minutes and try again.
Either way, if you tried to get it to light it several times and no luck, your system probably went into lockout mode. Since differant models use differant methods of resting it, check your owners manual how to do it on yours.