Tile shower floor leaking.
The reason it will not seal is probably twofold.
1. You are not allowing enough time for the moisture to dry out. The moisture is trapped and it has very little room to evaporate. This process could take a few days, a week or longer. You can speed up the process a little by applying heat directly toward the tile(heat lamp, portable heater, etc.).
2. The area that you are applying the caulking to must be thoroughly clean. All of the soap scum, mildew and dirt must be removed. A thorough cleaning, wash with clorox and finally a wipedown with isopropyl or denatured alcohol (there is no oil base in these products).
Once the above two are accomplished you can then apply your caulking or grout and the results should be satisfactory.
Is sanded grout better than unsanded? Seems that sanded would be more rigid and binding.
Thanks again, Jim.