You die of something like Altzheimers where the brain is degraded at death

Not all of what makes you you is encoded in the physical state of the brain

The current cryonics process is insufficient to preserve everything

You've then got to weight these things against how much you would count a less-than-perfect revival as a partial success. The me that's alive today, after all, is not the same person, in opinions, memories, even abilities, as the me of twenty years ago, but I still count both as "me".