I bought an Office chair and Officedesk1 (cheapest) and its not registered in the objectives when placed in HQ. If there is something else required if should be made clearer what you actually need and also where to get it (not listed in F1 help yet)
I figured it out myself, Mr.Scott’s Office supplies turned up after hiring a purchase agent.
I believe the store should be accessible without the purchasing agent. If it wasn’t, that might be a bug.
It’s also possible you just didn’t realize you needed to go there because you’re completely right: there is no indication of where you need to go to get stuff.
I actually just made a feature suggestion that would have probably helped your situation:
Hello! We’ve updated the tutorial on Beta 2 to specify that those items have to be bought from Mr. Scott’s.