New shower and tub install leaking

I have a leak in my newly installed shower and tub. Plumbing was redone by a plumber to accommodate a single handle from a two handle setup. Now i have a leak. I tested shower running with no one in the tub and nothing. I tested faucet running no one in it and no leak. Tested faucet running me standing in it and no leak. Tested shower running me in it and it leaks. All hardware has been removed and re-taped/putty and reinstalled. The hardware covers have been siliconed in case water was running behind it and down the wall. Now i still have a leak. Thoughts?? I cant see any leaks when the hardware was off.

Next plan is to take down the cedar ceiling in the basement bathroom to take a look but would really appreciate any advice.

have you tried calling the plumber back.....if its a new install he should warranty it

Not yet. Everything is covered right now so hoping to fix it without opening it all up. Im sure.they will fix it if the problem is with their work