Its more complicated than just buying a hose and hooking up to it.
Perhaps post the brand and model of BBQ plus if it is one that came with RV or one you had laying around..
Pictures would be most helpful for folks to identify potential issues.
The hose you bought, did it have a quick disconnect coupler?
Or did you buy a generic air (ones you would use for air compressors and air tools) quick disconnect coupler?
Reason I as is a propane disconnect may look like an air coupler, but it is not 100% compatible with propane coupler. There are differences between the two and the air coupler may not seat correctly either not opening the safety valve or a potential leak.
Now, generically, if you have a "aftermarket" BBQ that didn't come with the RV and that BBQ is designed to hook up to a 20 lb or 1 lb cylinder there are some complications you will run into.
Number 1 complication is the BBQ designed for 1 lb and 20 lb cylinders will already have a high pressure to low pressure regulator. Generally what some folks have done is remove the regulator on the BBQ but this doesn't always work 100% on all BBQs.
Your RV propane lines will already have a high pressure to low pressure regulator at the cylinders. Low pressure propane is required by the gas appliances on board.
In this case, feeding low pressure into a high pressure regulator results in the BBQ not getting enough or any propane.
You need to know if the coupler on the RV supplies high pressure propane or low pressure propane.. Generally though a fair chance the line you are connecting to is already regulated to low pressure but you may wish to trace the line back to the cylinders where the regulator is to be sure.
