Ok. Took the female connector off. No cracks that I can see. Came off real easy and the sealant seemed to come off easy too. Some sort of non hardening white stuff. The oring May have the faintest of marks. I’ll replace it, but what kind of sealant to use on the female connector.
Good question on sealant.
I presume that when you say female connector you are referring to the connector that screws into the raised boss that has the ring pressed on? (if not then disregard the below)
If you removed the fitting from the raised boss with the ring on it then you have to be VERY CAREFUL in how you reinstall it. That is basically a non removable part due to the ease of cracking the plastic boss at reassembly. If that fitting is overtightened, even a little bit, that can crack the plastic boss (even with the ring on it), but if it isn't tightened enough then it can leak. (there is no torque suggestion so it is a touchy-feely type thing).
To complicate it even more, if a PTFE or slick type thread sealant is used that makes it even easier to crack the plastic boss as those are a bit of a thread lubricant.
That white compound you are seeing is probably a PTFE type sealant (I don't think it is factory).
My personal fuel fitting sealant of choice is LocTite 1527514 Thread Sealant with PTFE but, as mentioned, you have to be ultra careful if using that type of sealant.
Do not use any type of Teflon tape as that definitely expands the lower fitting, also, pieces of the Teflon tape can get cut by the threads & end up in a fuel injector nozzle.
The down side to using a PTFE or Teflon based sealer is IF the boss is currently cracked then the sealer will temporarily seal the cracks so it will show leak free for a while only to start leaking if/when the sealer washes out of the cracks. (in finding white sealant as disassembly that might have been your leak problem)
CAUTION: DO NOT screw that fitting in any farther or any tighter than needed to be leak free or you could easily crack that plastic boss.
Personally, I would see if BMW will address the leak if it isn't just a fitting "O" ring leaking. If the leak is at the fitting to plastic boss then it s-h-o-u-l-d be covered by the BMW recall. If you mess with it too much then BMW might just blame you & not their poor design.
If that bike were mine I would first call my BMW dealer & explain the fuel leak, leaking area, & recall commitment. Depending on what they say & how receptive they are to addressing the issue (I assume they should warranty it). I would then reinstall the fitting using just the sealer that was there, then install a new "O" ring. If it still leaks then have BMW address the recall related safety issue.