If you use Sucuri for WordPress, your WooCommerce API may be getting blocked when Fomo attempts to access order data.
Here is how you can whitelist Fomo.
Go to the Audit trails and see what is being blocked. Look through the logs for a path starting with wp-json/wc/v2 or wp-json/wc/v1.
Once confirmed, visit Settings > Access Control > Whitelisted Url paths and enter the blocked path. The blocked path in this case may be /wp-json/wc/v2/ or ^/wp-json/wc/v1/.
You're done! Fomo should now play nicely with your Sucuri firewall.