HTTP status code: 403 Forbidden

Go to the profiler’s main page, click the “Support” tab and search for [admin-ajax].
Do you see [access] => OK or an error instead?

I think the problem was, that enabling Cloudflare’s “Development mode” is not the same as disabling the proxy by making the clouds grey ??
Thanks, now it’s working

You can try to bypass your CDN by directly accessing the site via its IP address and adding the host field:
1. In the “Page to profile”, select “Custom post/URL” and enter the server real IP address instead of the domain. For instance: https://1.2.3.4/some-page-to-profile/
2. Then click the “Advanced Options” button and in the “HTTP headers” section, enter the “Host” field with your domain name. For instance: Host: example.com

If you block IP addresses that don’t originate from the CDN at your server level, that won’t work.

Thanks for providing this workaround. Disabling the CDN for a test is not a problem.

If I need to test more it’s always better to test via the staging environment.