Error retrieving Domain Key

Hi,

I am having troubles with retrieving a Domain Key to link the website to the QUIC.cloud services. It’s days that I am losing sleeps on it, so I thought I might just ask for help. I have two other websites using LiteSpeed and never had this problem before. I am having the error message:

`There was a problem with retrieving your Domain Key. Please click the Waiting for Approval button to retry.

There are two reasons why we might not be able to communicate with your domain:

1) The POST callback to https://melbtraining.com.au/wp-json/litespeed/v1/token failed.

2) Our Current Online Server IPs was not whitelisted.

Please verify that your other plugins are not blocking REST API calls, whitelist our server IPs, or contact your server admin for assistance.:`

Website: melbtraining.com.au
Report number: FJZEOUFF

I tried to disable Wordfence but with no success. I am using Vultr, and there is no firewall set in there for that instance.

Thank you so much for your help,
Stefano