If you're having trouble with ALL of your URLs, try this article here: Validation troubleshooting.
Step 1 → Confirm that your signup links / attributes have been added to your site.
Step 2 → Publish your changes so they are live and accessible online.
Step 3 → Remove any password protection from your site.
Step 4 → Double check the URL you're testing. You may need to include the full slug, including folders.