Hello,
I had the same problem, I ran all the tests and there was no solution.
Finally, I solved it by disabling the WP Cerber Security, Anti-spam & Malware Scan plugin, it may be that the problem is due to this plugin or a similar one installed in WP.
I hope it helps you.
-WP Version 5.7.1
-WP Cerber Security, Anti-spam & Malware Scan Version 8.8.5
-SEO YOAST Version 16.1.1
Greetings.
