Hello @adtastic,
Thank you for contacting the support forum.
It looks like your host/server is blocking the request. You may try adding the following to your site’s .htaccess file to get it to work:
<IfModule mod_security.c>
SecFilterRemove 001868
</IfModule>
Or, you also may contact hosting support.
If still, the problem exists then will you please share your WordPress admin login credentials with us in a private reply so that we can debug and give you a better solution about it?
thanks