Upon checking further, it seems that our server’s firewall rules are blocking some requests for an unknown reason.
Changing the firewall rules on our server is not straight-forward and we will improve them over time. In the meantime, we would request you to please use our online tool instead of the SEO Analysis in the plugin: https://rankmath.com/tools/seo-analyzer/
We seek your understanding.
If there’s anything else we can help you, please let us know.