406 permission denied

Hi. I do have a wordpress blog since 2019 and had Yoast. I’ve read good thing about Rank Math, so I wanted to give it a try. The installation process was smooth, but soon I’ve found that in some settings (like “general settings” and “Image SEO”) if I try to save the changes (or no change at all) I receive the error 406 (Not acceptable).
Image:
https://ibb.co/6RFScj4

And I’m the administrator. And I can change “Titles and meta” settings. And never had this problem with another plugin. I tried to disable my plugins, one by one, to see if it was a conflict. It wasnt. I checked all the access in the “role manager”. No result.

Thank you.