Could be as simple as not using the correct size trowel the back of the tile has to be covered 90 percent with thinset.
Tiles not sticking to wall.
The wall has not been sized.
If the wall is wet the tiles will not stick.
Or take them all down putting wax paper between each tile so they don t get damaged.
Be sure to spray the wall surface with water to activate the glue.
Sometimes self stick vinyl tiles won t stick only after the fact.
Mixtiles are beautiful and attach easily.
Do not clean them with a solution that is gritty or has crystals in it as that could mess up the adhesive in the tile backing.
It is a good idea to clean them the night before you plan to do the tile.
Tiles arrive in five days and shipping is always free.
To fix a tile that pops up later reactivate the adhesive by heating it up with an iron.
The plaster finish is pink and very smooth but not dusty.
Use gorilla glue to replace each one.
The problem is the size and weight of the tiles first is the tiles porcelain if so they should not have been fixed to plaster walls and you should of use powdered adhesive ready mixed is only good for ceramic tiles up to 300 x 300 the walls should be clad with tile backer board including the smooth finished wall and any priming should be done with sbr diluted.
Tile won t stick to thinset.
Many people think that with peel and stick tile you should not have to use adhesive at all.
Cleaning your trowel frequently by washing it off with water will make it easier to work.
After 2 days can easily be lifted off by hand with no adhesive left on the wall.
Keep a damp rag handy so you can keep your hands clean.
Mixtiles are beautiful 8 x8 photo tiles that stick and restick to your walls without nails or any damage.
Just lay it lift it back up and check for coverage.