"George" wrote in message

For suction cups to stick to the tiles in a bathroom,the tile must be
thoroughly devoid of dirt and oils ie wipe with turps or meths.
The cups also must be cleaned.

The tiles should also have a smooth, glossy surface.
Some tiles have some texture that will allow air
to gradually get under the suction cup.

One thing you might try is a very thin coating of
petroleum jelly around the rim of the suction cup
to act as a gasket.