Tub still leaking after drain replacement..?

Hello,
The bathtub has been leaking so I attempted to change the pop up drain ( drain assembly). When taking the old one out, all seemed well. Rubber gasket was intact, very clean. The old drain had been sealed with caulk or sth. similar.

What I've done so far:
1. Installed a new drain using plumber's putty at the rim...still leaking.
2. Installed a the new drain using Teflon tape around the threads & silicone caulk....still leaking
3. Covered the rim with duct tape to check if it's leaking from the rim...still leaking.
4. ???

The ceiling is open from below and it appears that the area underneath the tub is filled with spray foam.

Would this indicate that the pipe is cracked somewhere?
Piping is PVC.

Any input would be appreciated, thanks.

Good possibility. Dig out the foam and take a peek.

Thank you...working on it....

It looks like the piece of tubing directly underneath the tub has a crack.

Is it possible to replace that smaller piece of pipe without replacing the pipe that goes to the overflow?

I'm attaching a photo.

Thank you for you input.