I still say that there is A LOT of stuff we still don't know here.
First of all, for background information for those who may not be familiar with US academic system (assuming that this is from a US institution), a new academic staff often enters a tenure-track position at the Assistant Professor level. Then, after a specified period of time, the department will evaluate if that person will receive tenure. If he/she does, he/she will be promoted to an Associate Professor. This is essentially a "permanent staff" position. A full professor position is another promotion when the department performs another evaluation and deems that this person deserves the senior position, and the university agrees.
Anyway, back to the issue. While this person may be in his or her 50s, did this person just started out in academia? This is because I don't know of anyone who has been denied tenure, but continues at the same school as an Assistant Professor. When was this person hired at the Assistant Professor level? If he/she is new, and has research funding, that is often the person you want to work with because he/she tends to be very active, and still very enthusiastic about the research field.
So, without knowing this, without knowing if he/she has funding, etc... etc., there's very little one can offer besides unfounded speculation.
Zz.