SG optimizer API issue

Hi I am getting the below error using SG optimizer:

COULD NOT CONNECT TO THE WORDPRESS REST API
Either a security plugin, custom function, or rules in your .htaccess file is preventing the WordPress REST API from working properly. SiteGround Optimizer is using it to store its options and other functionalities so please make sure it works properly.

I’ve deactivated AIOWS and the error with SG optimizer goes away. “Disallow Unauthorized REST Requests” is not checked. I tried emptying cache multiple times but no luck.

I’ve tried turning off basic firewall settings and cant see anything untoward in the database or file security.

Any ideas what setting could be conflicting? Or is it more than just a setting that will be conflicting?

Thanks in advance