Problem with thawing cells from liquid nitrogen?

I took out the vial of MCF7 cells from liquid nitrogen and then left it at room temperature for 30 min to thaw, then I added media+10% FBS and centrifuged to remove DMSO and then resuspended the pellet in fresh media and then cultured it....now it is almost 24 hours but the cells are not attaching. what is the problem?