However, this safety net doesn’t just catch attackers; it also occasionally catches misconfigured devices or devices with invalid login credentials. Our customers have the option to unblock themselves in their customer portal. However, it is essential that the customer resolve the underlying issue first, as another IP ban would only be a matter of time.

To make your search easier, we have compiled the most common causes of an IP block for you. This allows you to easily check where the failed login attempts are coming from and resolve them yourself.

1. Outdated login credentials

It is common for phones that were previously in use with an account to be brought back online, even though that account no longer exists or its password has been changed. This can happen quickly if, for example, you delete a virtual DDI in the customer portal but it remains stored on devices or in a softphone. If such devices are not reset or at least have their login credentials updated, their registration attempts will eventually result in a lockout.

What you can do: Depending on when the lockout occurred, consider which devices (including computers and laptops with softphones!) you most recently put back into service. Start there by checking the login credentials and correcting them if necessary.

2. Typos in the softphone

Whether in the username or password, typos in authentication credentials are a common cause of IP bans. Softphones are particularly prone to this issue, but hardware phones are not exempt either.

What you can do: Re-enter the login credentials on your devices. Start with the devices that were most recently put into service.

3. Test devices are not reset.

Phones are often configured in advance for testing. When the production connection is set up, the test accounts are deleted in the customer portal, but the devices and softphones are not reset. These devices then attempt to register using the accounts that no longer exist, triggering a lockout.

What you can do: Please check the login credentials on all devices you use for telephony. Start by checking the devices that were activated shortly before the lockout. For larger installations, it can be helpful to take most devices offline and bring them back online one by one to identify the source of the issue.

4. Incorrect installation of telephone systems

If incoming and outgoing calls are managed by a telephone system that performs a general registration, special care must be taken during setup. The complexity of most telephone systems creates a high risk of errors and makes troubleshooting difficult. For example, it may happen that although the login credentials are entered correctly and registrations are successful, incorrectly configured call signaling leads to a block.

What you can do: Please check your system configuration and verify that it matches our instructions exactly.

5. Call scripts result in too many call attempts

It’s not just registrations with invalid data or incorrect call signaling that can lead to an IP ban. Some industries have calls initiated by computer programs, with a human taking over the call only if the connection is successfully established. The result can be that the high number of call attempts is interpreted as an attack and met with an IP ban. 

What you can do: Find a reputable business sector or reduce the number and frequency of call attempts.

 

Regardless of the reason an IP address was blocked, please always try to determine the cause first. You can then lift the block in the customer portal. We explain how this works in detail in the article “Why can’t the registrar be reached anymore?”

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Created on: 12. June 2026