XB24-B can't be seen in XCTU 6.2 when configured as Zigbee Coordinator API mode

Hi I have Xbee Radios Series 2 (XB24-B), I used them with XCTU 6.3.2 in AT mode without any problem.
Now, because I have to do a star topology network (1 coordinator and 4 end devices)I need to go in API mode.

I started uploading the firmware of the AT coordinator in the first Radio and as a result XCTU 6.3.2 does not see the radio anymore.

However if I send packets to the radio through the UART it responds correctly, so I guess that there must be some problems between my radios and the XCTU when in API mode,
anyone can help?

Try removing and adding it back in.

What firmware version did you load on that module?

How is the module connected to the PC?

Doing some tests I found that the problem does not presents if I load a ZNet firmware in place of ZigBee one.
Maybe simply my radios are too old and do not fully support Zigbee