Look to see if your new cooker has a gas regulator attached. This will be where the gas connection would be. If you see a regulator, then you will have to remove it and plumb it correctly to connect to your supply line. Many aftermarket cookers, grills, etc. are set up with a regulator, so you can use the high pressure canisters. Your rig already has that regulator somewhere near your propane tanks.
One more possibility, your new cooker is prepped for natural gas, and not propane. If set for natural gas, then you need to get the different orifice that will allow you to run it off propane. No matter what you do, when you are done, double check any changes you do for leaks!!!
1987 Starcraft Nova tent trailer, purch. '87, sold 8.14
2013 Crusader 290RLT bought new, 8.14
2001 Ford F-250 7.3
A Loving wife and Mason the always dirty dog!