Does the free trial apply to all my workspaces?

The 7-day trial is granted once per person, not once per workspace. At checkout you choose which workspace to upgrade, so you decide where your one trial lands, but it only attaches if you are still eligible. Each workspace carries its own subscription, yet your trial eligibility is tied to you, so upgrading a second workspace later charges you immediately, with no new trial.

Billing is owner-only, so you can only start a trial on a workspace you own. Joining a workspace that is already Pro (as an invited member) does not give you a trial; you simply occupy a paid seat. The trial only applies when you upgrade a Free workspace you own. A previously-Pro workspace that has dropped to Free can trial again only if you, personally, have never used your trial.

See why didn't I get a trial and free trial.