Dumb question...is your tank valve all the way open?
Another thing that comes to me is maybe your leak protection valve is engaged....
Close both tank valves and run the stove until the gas is bled out of the lines.
Start with the tank that the changeover valve, if equipped, is set to. Crack the valve just a little for about 10 secs, then SLOWLY open the valve the rest of the way. Repeat for the other tank (no need to change selector switch).
Use the stove to bleed the air from the line. I use a lighter at the burner until it lights.
See if this helps.
If not, you can try this (if you feel comfortable).
Close both tanks, bleed lines, remove the offending tank and take it to an open area free from flames. Wear a pair of gloves is best.
Point valve opening away from you and using the gloved hand, open the valve rapidly. Don't point it at your face or anything. Gas should come out very fast at first and quit after about a second.
Close the valve and wait about 5 mins, then put it back on camper and remember to open it slowly.
If the valve is 'sticky' this can force it to slam shut, which *may* help your problem.
OTOH, if both tanks make the noise, it is probably your regulator.
