Inspect the flooring tiles to determine the exact locations of those that appear loose or lifted. Mark these tiles with a washable marker so you do not spend too much time looking for them.
Spread a cloth over the marked tiles until they are completely covered. Bring your clothes iron to medium-hot setting and slowly rub it over the cloth in a circular motion to help soften the adhesive.
Insert the tip of a putty knife under an edge of the tile and slide it across toward each corner, loosening it from the floor. Iron the tile again if it remains stuck.
Lift the loosened tile from the floor and set it aside. Repeat the process to remove the remaining uplifted tiles from the floor. Inspect the tiles for damage, and replace these with identical ones instead of reusing them.
Spray mineral spirits over a rag and rub it on the adhesive behind the tiles and on the subfloor until soft, so it is easy to remove. Scrape the loose adhesive off the tile and floor with a putty knife. Rub remaining adhesive behind the tiles with sandpaper until the surface is completely smooth.
Apply a thin coat of flooring tile adhesive over the back of a tile before lowering it in place. Press the tile to help the adhesive adhere to the subfloor and remove trapped pockets of air. Check that the tile falls at the same level as the surrounding tiles, or add more adhesive underneath, as required.
Wipe away excess adhesive from the sides of the tile with a clean rag. Repeat this process of laying the remaining tiles over the floor. Ensure this repaired flooring section is at the same level as the surrounding floor.
Loosen and remove the grout around ceramic tiles with a putty knife and hammer. When loosened, slide the knife under the tiles to raise them from the floor.
Scrape away loose mortar from under the tiles and the surface of the subfloor with a putty knife until smooth.
Prepare mortar according to label directions and apply a small amount on the subfloor. Spread it with a notched trowel before placing the tiles over it, spaced 1/8 inch apart.
Check that the tiles are at the same height as the surrounding tiles, or adjust by adding or removing mortar from underneath. Allow the mortar to thoroughly dry according to manufacturer's instructions.
Insert grout into the gaps between the tiles with a rubber float. Wipe the flooring surface with a damp rag to remove excess grout after one hour.