I have 3 Macs:
2011 27 iMac ("A")
2011 27 iMac ("B")
2011 13 MBA ("C")

Airdrop works between A and B, A and C but not between B and C.
The only difference is that "C" was installed using migration tool from "B".
Could this be the reason and what would be the solution?
Do both B & C believe they are the same computers?

Any idea?