presence isn't changing for one user. it appears that the only time it changes is when the user changes it manually. he says he's never signed into Lync on a mobile device, and a password reset has not effected the issue which suggests to me that there is no other device configured with his account info, aside from the PC he's currently on, that could be skewing the results.
had him login, set presence to busy, and log out. the other end sees his busy status, and as the user logs off, his presence reverts to available rather than offline. (???)
I have access to concurrent repro logs ( uccapi and ETL ) from both ends of a successful repro, but I have no idea what to look for regarding this as I've never seen anything like it and I'm pretty new to reading them as it is.
any suggestions as to a starting point/things to check?