There is an oddity in the way the sign in for 3D Warehouse and other features work, compared to being signed in as a Classic user. If you were a subscriber, every 28 you would need to sign out and back in again. As a Classic user you don’t have to do that, but, the warehouse and add location windows are using the subscription method for signing you in.
Which means that even though you are still signed in within SketchUp, do a sign out, and sign in again, and those features should work for the next 28 days.
By the way, you still had support until April 2021, which means you have a SketchUp 2021 license that you haven’t used yet.