There were recent outages from Anthropic, Openai and issues with Gemini but the situation should be improved now.
If the issue remains could you check following and let me know more details as this should be reviewed in detail and solved.
Did you use any MCP in the chats that stopped?
Is an API key active in your Cursor settings?
If you can reproduce the issue, please disable for a request the privacy settings and post here the Request ID, this will help the Cursor Team to have a look at the details and investigate the cause.