Searching from tapatalk won't work, so it's been disabled.
Probably the simplest solution, though it would behave differently from the default vbulletin search, would be to change searches through tapatalk to use google.
A more complicated solution would be to get tapatalk's search to use the same sphinx search backend that the rest of vbulletin uses.
I'm thinking about buying tapatalk so I can work on one of those options. However, tapatalk needs to die, and vbulletin needs a nice mobile css skin. Unfortunately, unless there's a free one on vbulletin.org or something, that's probably more work than the alternatives of just fixing tapatalk search.
“The egg hatched...” “...the egg hatched... and a hundred baby spiders came out...” (blade runner)
“Who are you?” “A friend. I'm here to prevent you from making a mistake.” “You have no idea what I'm doing here, friend.” “In specific terms, no, but I swore an oath to protect the world...” (continuum)
“It's a goal you won't understand until later. Your job is to make sure he doesn't achieve the goal.” (bsg)