change antenna on XBEE 900HP

I have some XBee 900HP S3B with wire and UFL antennas. I need to convert to SMA. I have installed the SMA connectors but it does not work, the transmission works only with the xbees right next to each other like when there is no antenna. Is there any way to fix this? I done care about FCC or warranty as I live in another country.

No, there are different components that are populated during manufacturing for the different antenna types.

You also need to be aware that if the radio is not certified for use in the country you are in, you may not be allowed to operate the device at all.