A corporate office is not like an administration building at a soft-handed university. There's no way you are going to successfully take over an office for any real amount of time unless you are willing to use real violence and potentially get into some kind of hostage situation.
The police will be called, there will be more of them than of you, and they will remove you.
Protest is a show. You don't need to take over for days, you just need the protest to have maximum reach which in our time could happen in minutes. Obvious things they should have done : Inform their colleagues beforehand, so they be in the know, plan around it, and why not participate in some form. Inform journalists and smuggle them into the buildings. Police intervention is planned for and should be a major part of the show.
Journalists know better than to get involved in something like that. They would be asked to leave immediately (it's super easy to notice people standing around filming what's going on who aren't wearing employee badges), and then they would of course leave immediately as they aren't willing to catch a trespass charge just for one page 17 news article.