My company has used the Xbee Pro S2B in our products. I have a test setup with several of these in it.
We were told that S2B will be going away and were steered towards the XB24C as a replacement.
I replaced all of the client Xbee in the test setup with XB24C and kept the S2B as the coordinator. Everything worked great. Then I tried replacing the coordinator with XB24C so that all radios in the setup are XB24C. It did not work at all. Even with "CE" set to 1, and the OP of the new radio set to be identical to that of the old S2B radio, the new radio cannot find any of the client radios.
If I go back to the old S2B as coordinator everything works just fine. If I try the new XB24C again then nothing works. I assume that I have a configuration problem with XB24C but I am unable to determine what it might be.