What to include
Style Capture does all its work in your browser and sends nothing anywhere, which is good for your privacy and unhelpful for me: when a capture goes wrong, there is no log on my end to go and read. So the more of this you can put in the email, the faster it gets sorted. The URL of the page you were capturing, roughly which element you clicked, what actually landed on your clipboard, and what you expected instead. A screenshot with the highlight over the element is often enough on its own.
Things that are not bugs
The extension can only see a tab once you have clicked its toolbar icon. That is the activeTab permission working as intended, and it is why nothing happens on a page until you start a capture. Chrome also blocks extensions outright on its own pages, on the Chrome Web Store, and on a handful of other reserved URLs, so a capture there will fail however many times you try it. If you need styles from a page the extension cannot reach, the CLI and the agent skill capture the same thing from a headless browser instead.