contractor- tiling fiasco

Need some feedback. We have a contractor in resurfacing our kitchen- new cabinet doors, countertop, etc. We are also tiling on tile (floor). I know tiling on tile is not ideal, but our contractor said he could do it (multiple times)- "no problem". Well, the workers laid down the tiles yesterday, but 24 hours later the cement has not dried at all. You can actually pick the new tiles up off the floor- the cement still looks like cake frosting. So now they are back in the kitchen removing the tiles, scraping up the wet cement and are planning to use a cement that is "quicker" drying. (The cement they used yesterday was supposed to be quick drying!). I tried to discuss this with the contractor but it's very difficult b/c of language, mobile phone connection, etc. I find it weird that the cement didn't dry at all- it was some kind of acrylic cement from France. (The kitchen looks good otherwise, but tiles have been a disaster). Does anyone have any comments? Are these guys not doing something they should be doing? I'm very frustrated (haven't been able to use the kitchen for 5 days, going on 7 now) and don't know what to do next.

I had Tiles placed over existed tiles in our home In N Z in Aug...heres what the contracter did.

First sanded the tiles with a grinder, put a certain mixter of glue and concret down. I was told that if the old tiles where not ground first then the new tiles would lift.

thanks for the replies. For some reason, the contractor decided to use a new type of cement for this job. They also applied it a bit too thick and it was just going to take too long to dry. So, they took the tiles and old cement up, bought a different type of cement and relaid the tiles yesterday. The tiles are dry today and seem solid. I'm just happy that they were quick to respond to the problem, rather than wasting time making excuses or waiting to see if the tiles would dry. Hopefully all will turn out ok.