I’ve noticed sometimes I need to factory reset the OB-4 to connect with bluetooth, especially when I get a new iPhone. This happened more than once, generally when I upgrade my iPhone to a new model. Something about the protocol just seems to subtly change, and it absolutely will not pair until I reset the OB-4.
Which is not a big deal, just frustrating because one moment it’s working (with your old iPhone) and the next moment it’s not (with your new iPhone). I’m sure it’s an Apple thing, but I also can’t think of many bluetooth speakers I have this problem with?