> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/products/cloud-services/command-centre-mobile-client/troubleshoot/mobile-client-http-error-503.md).

# Mobile Client HTTP error 503

Diagnose HTTP 503 errors when Mobile Client connects through the Gallagher API Gateway.

HTTP Error 503 affects all clients connecting via the API Gateway. It is usually **not** a Gallagher cloud or Command Centre configuration issue. Something in the site environment is blocking a secure TLS connection to the cloud.

Check [Gallagher Status](https://status.gallagher.com/) first, then check for:

* Wrong **clock** on the server
* Broken Windows security settings, for example TLS 1.2 disabled in SChannel
* Anti-virus or endpoint protection intercepting or inspecting the TLS connection
* Network firewall or security device intercepting or inspecting the TLS connection

For the required ports and addresses, see the Cloud API Gateway Technical Information Paper.

***

🔗 **Related**

* [Mobile Client trouble connecting to the Gallagher Cloud (8.60+)](/knowledge-hub/products/cloud-services/command-centre-mobile-client/troubleshoot/mobile-client-mobile-client-trouble-co.md). The API Gateway connection path.


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