If you or someone else tries to log in to 3CX more than once with the wrong credentials, 3CX will block access from that IP address. This is done to protect the 3CX communication system from future malicious demands. In this case, you will see the following message: The IP address that was blocked and caused this ban could be one of the local IP addresses of your computer, IP phone, or mobile phone. When hosted, external IPs for Internet access are blocked. This will prevent all users using the same IP from accessing 3CX. How to unblock: To remove a blocked IP address: Requires administrator access to the CX management console Log in to the 3CX Management Console from another unblocked IP address. If 3CX is on the network, use another PC. If 3CX is in the cloud, use your mobile data plan (disable WiFi!). After logging in, go to 3CX Dashboard-> Blacklisted IP Find the IP in question (you may see a lot of legitimate blocked addresses here) and press Remove. Prevent future blocks: To prevent this particular IP from being banned in the future, remove the entry. Then whitelist the specific IP. Change Block to Allow to specify that this IP should be allowed. This is useful, for example, in a static field office. Use with caution as 3CX will no longer trigger the anti-hacking feature on this IP. Only allow trusted and trusted IP addresses.