Problem #

After you save valid settings for the E-Invoicing addon module, a banner displays the following message:

The system failed to synchronize the account with the e-invoicing service.

Cause #

This issue usually occurs for one of the following reasons:

• The License ID or License Key is incorrect in the E-Invoicing settings at Configuration () > System Settings > Addon Modules.
• A temporary outage at the e-invoicing service prevents synchronization.
• A network issue prevents the WHMCS server from reaching the e-invoicing service.

To identify the cause, go to Configuration () > System Logs and review the Activity Log.

Solution #

To resolve this issue, identify the logged error and follow the appropriate steps:

• Authentication error (401) — The license credentials are incorrect. For steps to resolve this issue, see E-Invoicing License Errors.
• Server error (5xx) or connection error — There is a temporary service issue. Wait 15 to 30 minutes, then save the settings again to start a new synchronization.

If authentication errors continue after you verify the credentials, or if server errors continue for more than two hours, contact WHMCS Technical Support.

Last modified: 2026 September 17