Do you have outside leveling switches? If so, unlevel or level the coach. They can get jammed due to a skewed door frame during leveling or parking on unlevel surfaces.
What type of lock? Can you upload a picture?
If the temp is under 35F then you might have a frozen or stiff lock problem. They make lock de-icer... or you can try WD first.
or use 91% Rubbing Alcohol from Walmart
or heat your key up with a flame and then insert a few time so the heat can transfer... and try the key.