Sealers should never be applied on heavy; particularly on dense materials like glass tile and some dense stones. They should be applied lightly and wiped dry within 5 minutes to avoid tacky surfaces that can result in maintenance problems.
Sealers don't make the porous grout or porous stone waterproof, but the water should readily bead up on the tile surface with a tight meniscus if the sealer is working. I would not expect it to leave a wet spot on the stone surface after only a few minutes.
One sealer known to be of good quality for this use is Miracle Sealant 511 Impregnator from the Miracle Company. You can find their website link, as well as those of other sealer manufacturers on our website at Cleaners & Sealers Resources. If you decide to try another sealer you need to make sure it is compatible with the sealer you have already coated the tile with or you may need to strip the old sealer. Make sure that the tile and grout is fully clean and dry before applying the sealer.