Redirections stopped working. REST API problem?

I have a simple one page site running Redirection. The redirects were working fine but for various reasosn I deleted and reinstalled the site, and now the redirects don’t work. I am getting the warning ‘There are some problems connecting to your REST API. It is not necessary to fix these problems and the plugin is able to work.’ Could that be the problem?

I am running All in One WordPress Security. It has a setting called ‘Disallow Unauthorized REST Requests:’ but that is not enebled. I have tried turning off all the Firewall settings but that doesn’t help.

Hope someone can help; I’m about to go away for 2 weeks!