First set them both on one channel 20Mhz wide. Both ends the same and do a scan before to see if that channel is free. Then do a aligning on both ends to get the best signal. But the radio’s can take up to a minute to connect, longer even after a powerboot. So patience is needed too.
If everything is on auto it might take too long for both radios to get connected, and if the units are not aligned properly yet you just won’t get a connection.
Another trick to play under difficult long distance high gain (=narrow beam) antennas is first to use two simple radio’s (ubnt, mikrotik any other). First with two log rubber duck antennas on both conectors make sure you have a working link on your worktable in the lab.
Then connect these radios on the two dishes in the field and start aligning until you get the best signal.
Only after that is done replace them with the Mimosas. Would be rare if they’d still don’t connect.