Perhaps the answer given is the wrong answer. New silicone sealant won't bond strongly to old cured silicone sealant which makes for a lot of work cleaning out the old when a redo is necessary. That has nothing to do with ordinary bathtub caulk not drying even if it doesn't stick to anything.

As a nonexpert diy I have two areas of concern: if you have any Dap left, run a bead of it on a piece of wood or something and see if it dries normally. As to prep, after a normal but thorough cleaning and drying of the tile/tub area adjacent to the intact old caulk, I remove it. I usually only use a razor scraper on tile and enamel, a small tool on grout, and a short spray from a spray bottle of 90%+ isopropanol along with a microfiber cloth to carefully clean the surfaces to which the new caulk will stick and dry.

I agree on every point. First, what you've described with the DAP is vey characteristic of old caulking. As for cleaning out the old silicone (and I wouldn't be surprised if that's the case) you can go to just about any hardware store, and they'll have a solvent for getting rid of all traces of old silicone. Once that's done, you can use whichever caulking you want, although my choice is for siliconized latex.

THanks guys. This week I'll get back to it.

Tom