Ceramic floor tiles can come loose for a variety of reasons. Being that yours were just installed, the two most logical would be either the thinset used was allowed to skin over and dry before the tiles wetre placed, therefore not allowing the chemical bond to take place that holds them in place or, the subfloor was improperly prepared and cannot support the tile installation.

If the thinset dried before the tile were plced, you can remove the tile by carefully removing the grout around the tile so they become independent of the tile next to them. Slip a putty knife into the channel made in the grout and work it under the tile. The first one will be the hardest. It should pop up. Do this to all loose ones. The old thinset needs to be removed and replaced with new on both the back of the tile and the floor so the new ones can bed prpoperly in the new thinset and not ride high or uneven. Do not use any kind of glue.

What kind of flooring is under the new tile,wood or concrete? If wood, describe the layers as well as the size of the joists, the spacing of the joists and their length of unsupported span.

If cement, was there paint or a sealer on the floor?

the installer used the cement borard or whatever the material is you're supposed to use. Under that is plywood. I belive he must have let the bonding material dry too much and that is the problem. Thanks for advise on not using any glue, thats what I was about to do!