Error message: "Insufficient_quota You exceeded your current quota, please check your plan and billing details"
This message is unrelated to the extension and comes directly from OpenAI (we are not affiliated with them). The extension is free, but their API usage is not. It means that the free credit have expired and you need to update your payment method. Please visit OpenAI`s Billing page.
GPT-prompter option in context menu is visible but not functional/active.
Short answer: Try to reload the page.
Long answer: The extension has a way to check that all necessary components are running (in particular the content script). On some website, e.g. the Chrome Web Store, it doesn`t run by design (by Google). Other times, there might be an extension update and a simple reload of the page should fix the issue.