Marble tile over concrete floor

My installer did a beautiful job laying 24x24 marble tiles over my conrete floor in the bath, closet and hall area. However when he got to the bedroom, I immediately started developing loose and hollow sounding tiles. He says he did nothing different but it is because the 'concrete was polished' in the bedroom and that's why it didn't stick. So my question is 1) could he have seen the concrete had a different surface 2) is there another reason why these tiles are loose? Help please!

It's hard to say with out seeing it myself, but I would think so.
If the tiles are stuck every where else but that one room, it's probally cause it was polished.

The slab should have a fine broom finish with no curing compounds or other coatings on the surface. If a grinder was used to give the floor a polished look that would be bad enough because the pores would have been clogged up enough to not allow proper bonding of the thinset. If the surface was actually polished with a wax then that really doomed the tile floor

Thank you for your responses. My entire house has marble tiles, and it is only in one bedroom that the problem arose. The installer fixed 3 tiles that were really bad, and so far they are sticking, but there are plenty of others that are slightly loose. Will they get worse over time?

A 100% Yes!

So should I just wait till they all become 'unglued' and hopefully be able to remove and reinstall them? What prep needs to be done to fix the cement? One other thing - the installer had put about 5 blobs of mud, about 4 inches in diameter, and did not trowel it flat. Does that method of placing the mud make a difference in any of this?

One other thing - the installer had put about 5 blobs of mud, about 4 inches in diameter, and did not trowel it flat. Does that method of placing the mud make a difference in any of this?

YES IT DOES. The "five daub" method is a legitimate method but only for use on tiles being applied to walls and vertical surfaces. It should never be used on floors. Using this method on floors will guarantee that tiles can break over time. This method obviously creates voids behind the tiles. The (rules) say that floor tiles should have thinset spread so as to create an 85-95% bonded relationship to the substrate.

This installer is way off base.