Hi Anne,
Condos can be complex, because some work directly benefits an individual owner, whereas some construction work is done for the association, and serves the whole property. Often, things like roofing, exterior lighting, and landscaping improvements are commisioned by the condo association because they serve the whole community.
Feel free to take this into account when deciding who to send your notice to. Who called you to come do the work? Who do you expect to be paid by? For more, here's another individual who got an answer to a similar question: https://www.levelset.com/payment-help/question/does-a-lien-need-to-be-placed-on-all-units-in-a-condo-association-or-just-on-the-association-when-the-board-signed-our-contract/
Best,
Emily