Why don't I see any devices in the mobile app?

Error pattern:

Devices are displayed in the Mobile App for IOS, but not for Android.

Important: If no devices are available for IOS and Android, something seems to be wrong with the basic configuration. In this case, please check the setup again using the documentation: 

https://help.c4b.com/xphone-connect-9/doc/en/admin/config/srv/cfg/cfg-general.html#mobile-app 

Typical cause:

The certificate used is a legacy certificate that supports older Android systems. The disadvantage of these certificates is that they are regarded as faulty by newer Android systems.

You can check this with the SSL Checker from the WebApi Tester. In the case of a legacy certificate, the following message would appear:

Possible solution:

To solve the behaviour you need to replace the legacy certificate with a non-legacy certificate so that newer devices can also see the devices.

Explanation / solution from Certify The Web: https://docs.certifytheweb.com/docs/kb/kb-202109-letsencrypt/#switching-to-chain-1-modern