Hello,
Thank you for contacting Rank Math and bringing your concern to our attention. I’m sorry for any inconvenience this issue may have caused you.
Please note that you can only choose between noindex or index, as that robots directive should be present by default. Meaning, that they can’t both be unchecked when setting up the robots meta tag.
However, if the nofollow box is affected and not saving as well, please check if you are using a Firewall as it may prevent saving the changes.
If you are using a Firewall, please whitelist this route:
/wp-json/rankmath/v1/updateMeta
/wp-json/rankmath/v1/saveModule
You can check this link for more information:
https://rankmath.com/kb/meta-data-not-saving/
Let us know how this goes.