Gotta finish the Office questline making sure that Ryan is in power. It's been a while since I've played, but you have to get each of the office members to trust you. Angela is pretty easy, just babysit her cat, then follow the instructions, to get Jim, you have to get Michael first. To do that, you have to go out on business trips with Michael and "seal the deal" whenever the client asks you for a sexual favor. Eventually, Michael will let you go on business trips by yourself, and then you sabotage those deals. Eventually you'll be able to progress with Jim after that point.
If you follow all of Ryan's instructions then the office will be re-structured, and so will Jim.