I have a sewer smell contained in my downstairs bathroom and I can't figure out where it is coming from. I have taped up all drains but the smell still exists. How can I find and stop this leak.

Did you tape around the base of the toilet? You might have a ruptured wax seal.
Let me know, Tom

You need to make sure that there is water in the toilet, shower, or in the vanity ptrap. The water in the ptrap prevents the sewer gases from coming out and stinking up the room

Beaver,
Your answer's unnecessary. The Op already told you the drains were taped up to check them and the smell still persists.

Sipsac, Any gurgles in the traps when you flush or drain? Regards, Tom