Combox is your bluetooth box. I have seen this happen on a couple of my combox that I got at junkyards. First, delete all paired phones from the X5. Then delete the previous parring on your phone. And re-pair. If it does not pair and say successful, then the combox may need to be reset.
I believe the issue is old pairings that are corrupt and you can no longer see them in the list of available devices. ISTA+ software can do a force delete of pairings. If that does not fully fix, NCS Expert can write a blank MAN file to reset the configuration. NCS can't delete the old pairings so ISTA+ must be used for that.
You could find a local BMW coder on facebook who can fix this in a few minutes.
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