I’m on Unity 2021.1.21f1, and I have both the UI Builder & UI Toolkit 1.0.0-preview.17 packages installed. When I press play, my UI document does not have any styles. I’ve tried adding them manually by getting a reference to the root element, but it doesn’t appear to make a difference. Is this a know bug, or am I missing something?
Do you get any kind of error in the Console? Is it possible that some assets were not imported properly? You can try a reimport of your UI assets to make sure everything is fine in your files.