I remember there used to be a free Team workspace in my account

Ah, I see then I misunderstood the main part of your question. Sorry for that.

If you are seeing an actual free workspace in your account, but cannot manage or use its permissions, that sounds more like an account-specific workspace state or provisioning issue than something the public Business docs can fully explain.

That may need OpenAI Support to check the account/workspace state directly.

https://help.openai.com/en