If the firepit has a standard Acme screw on gas connection (tank end), those have an internal check valve that won't allow full flow until the pressure has equalized.
A crude sort of test as to whether it's working properly can be done by "ear". Here's how, now quoting from
this link wrote:
Inside the Acme nut, there is a ball bearing check valve that almost shuts off momentarily when full pressure is released by opening the cylinder valve. You should hear a click at that point. It doesn't shut down completely, as that would negate its ability to detect leaks and excess flow from a leak or major line break, and no gas could flow. It closes just enough to allow a bypass of gas that is very slight, about 10 cubic feet or less per hour (cf/hour) flow, as opposed to the max flow of 200 cf/hour. The bypass gas goes into the propane system, and if there are no leaks or broken pipes, it backs up and builds pressure in the gas lines in the RV. When it equalizes on both sides of the valve, the valve opens to allow full pressure up to about a max of 200 cf/hour at 100 psi. Then if you were standing there, you would hear a second click.
