I guess my overzealous comments on that stuff was really meant to be a heads up to anyone that was going to rush out and buy it, not knowing about the very strong odor and the inability to remove the smell of it once applied. Especially if used in the small confines of an RV. :C
To the OP: A gray tank can smell just as bad. You might be attacking the wrong tank! And/or the water in the p-traps in the bathroom sink went dry from sitting and your blank tank smell if coming up from there. Same thing with the kitchen sink p-trap if dry also.
20 years here of one bottle of blue stuff per tank. Dump, fill with water, dump again. No hosing no hockus pocus treatments, p-traps always full. and NO smell in the RV. Just saying.