First, try uninstalling / reinstalling the extension.
If the extension continues to fail in connecting, please provide LimaCharlie support team with details by doing the following:
1. Open a new browser tab
2. Go to chrome://extensions/
3. Ensure "Developer Mode" is enabled (see toggle in the top right)
4. Click the background.html link in the LimaCharlie Sensor entry
5. In the window that opens, click Console and provide us with a screenshot of what appears for analysis.
Please also include your organization ID, which can be found within the LimaCharlie web interface in the REST API section under OID.