If you have fuel coming out of the carb when you prime the engine, it should start.

I had a heck of a time getting my TT .46 to start before I broke it in. I had to use an electric starter. I'm not sure why you were able to start it with a different tank.

Try blowing thru the vent (exhaust) fuel line on the offending tank to make certain you are getting a positive flow out the carb side fuel line.

When you connected the second tank, was it sitting on top of the fuselage? Was anything else different besides the size of the line?

Sorry so darned many questions, it's just hard to figure these things out without a visual sometimes!