I have a custom board that accepts the XBee S2C or XBee 3 module of the same form factor. It's got an FDTI chip on it for USB to serial communication with the module. XCTU discovers the XBee 3 module, but does not discover the S2C modules. I verified that the serial input is getting to DIN, but I get no response from the S2C module. This is consistent with numerous boards.
Any ideas as to why the XBee 3 module is discovered and the XBee S2C is not?