If you are using the Members plugin to manage the permissions of your roles, you may run into the issue where your current user cannot access the settings of the Gravity Forms for Klaviyo plugin.

In the Members plugin, you can edit your Role and go to the GF Add-ons section and then grant that role permission to access the Klaviyo: Add-on Settings allowing whatever user roles you like access to manage the Klaviyo feeds and settings.