The A2Billing VPS template (A2B100) includes several security measures to protect your server. These include –
To whitelist IP addresses so that you can access the admin interface, and prevent IP addresses from accidentally getting blocked, you can run the following script, providing it with the IP address to whitelist –
Obviously change the IP address for the one you want to whitelist.
Alternatively just open a ticket in the support system asking for this to be done.