I have the same problem as well as a similar problem for sentinel vule. I will go to talk to them, not get an "A" totalk, then after I check my map the icon to talk to them is gone. If I do a mission and return, they have the icon again.
I have something similar but I see a conversation bubble on her head but no F key or means to communicate with her. See attached. Also, Im on a PC with RTX 2080 Ti and 16GB RAM.
Brin sometimes listens to her favorite radio show. That is when she will completely ignore you. You will have to wait until the show is finished, which usually takes about 10-20 seconds. Don't be rude, let her finish her business!
I've run into this too on Xbox One.
I've found looking at the sentinel rep, then the contracts board seems to then allow me to have a conversation with Brin if one is marked and I can't access it.
Not sure if that works every time but worth a shot.
This is still an issue. Not to mention that I had no clue I had story missions left over since there is literally no user feedback in this abysmal console UI