I installed a new faucet and tail pipe in a bathroom sink. It leaks where the tail pipe collar connects under the sink. I have done this type of bathroom faucet replacement probably 6 or 7 times over the years, so I know you can under tighten and over tighten the collar under the sink - the rubber gasket can get out of wack if you tighten the collar too much. But even knowimg that I can not get it to stop leaking right there. I have dismantled all of it a couple times, reapplied a rope of plumbers putty each time up top, made sure the new rubber gasket is inserted properly, tightened it down, and it still leaks.
I have no other ideas and it is getting frustrating. Yes I could call a professional out but I feel like I am so close. Plus I have to do the other sink’s faucet next (it’s a double sink countertop). Any ideas?