This is a change from openAI side that tries to block extension. It mostly affects GPT-4 model.
You can see the details for the issue here
https://community.openai.com/t/seeing-detected-unusual-activity-from-your-system-error-message-when-testing-local-plugin/252350

We are working on resolving this as fast as possible. In the meantime, can you change the model to be GPT-3.5-Turbo and that should work ?