Does your auto switch valve show green when you open both tanks? Are you opening both tanks? If not, is the lever pointed to the tank that you do have open?
I had a gas BBQ that if you turned he knob too fast, it would 'lock' the safety valve... I had to take the hose off, put it back on, then open the tank valve really slow to keep it from tripping.. (I don't have that BBQ anymore. :) )
I have never had that problem on my TT.. It's over 16 years old and the auto switch over works like a charm and I've never had flow issues with it.
Good luck!
Mitch