In ground gunite hot tub stopped blowing Air

Hello all, the title says it all, I have a in ground gunite hot tub that has stopped blowing air through the jets. The tub is connected to a pool as well, I have tried blowing air through the 2" venturi tube with a shop vac. as recommended by the local pool companies and no luck. I also fed a sewer snake through the Venturi tube and found no blockage. I have had 4 pool service companies out and they all tried the shop vac. and had no luck. Can anyone help PLEASE


Hoodride