I would start with easier possibilities first. Even if they are not as likely.
First thing I would do is turn the grill on and let it set for a minute or two before lighting it. This will tell you if actually lighting the grill is causing the problem or it is just a lack of gas flow after a few seconds. It may not answer the question, but it is quick and easy and will provide more information.
Then, I would start at the tank itself. Swap in a new (different) tank and see if that changes anything. The OPD in the tank could be malfunctioning. Again, very easy and quick. After that it is going to get a bit more complicated and you will have to move on to the hose, regulator, manifold, valves and burners