Log in with your JetBrains account if needed.
In what circumstances is it needed vs not needed?
From https://www.jetbrains.com/help/fleet/ai-assistant.html :
Under the hood, JetBrains Fleet uses large language models through JetBrains AI Service. The AI features are provided free-of-charge during the preview phase. To start using them, you only have to log in using your JetBrains Account
Sounds like it's always needed then. And it's going to be a paid subscription at some point.
Dear literally everyone trying to integrate AI into their products: cut the crap with cloud services. Just let us bring our own LLMs.