We are aware of an issue with SketchUp for Web which is causing some users to be stuck in a “verify if human” loop, or to have the service not fully load.
We’re hard at work to resolve the issue as quickly as possible. Our engineers have identified the root cause and are working to issue a fix.
You can visit our status page for additional information here: https://status.sketchup.com/
For any questions or concerns, please do not hesitate to contact our support team here: Contact Support | SketchUp Help
Note: Support is only available for users with a paid subscription.
Edit: A fix has been deployed, and SketchUp for web appears to be fully functional. We are monitoring the fix.