...
Make sure that the custo diagnostic service itself is allowed to communicate properly with the internet / the evaluation center. A test of the evaluation center URL with the web browser of the server may give a hint, but not necessarily needs to be a proof: The web browser may use a proxy server or have rights defined in a local firewall or virus scanner. Best test if the evaluation center URL is reachable via the smart phone and if so contact the admin of the server,
Another reason maybe that the server may not trust the certificate of the evaluation center. In this case open one of the system browsers (Internet Explore or Edge) on the sender's server and open https://letsencrypt.org/. Afterwards restart the custo diagnostic server.
Certification path not found
The sending pratice cannot connect to the evaluation center with an error like:
com.sun.jersey.api.client.ClientHandlerException: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
In this case open the .dtconfig file of the evaluation center with an editor and copy the URL of the evaluation center. It should look like "https://08155f6db5a913cfc77e454eb53f1a9.dyn.diagserver.customed.de:18443/diag. Then connect to the custo diagnostic server and open there one of the system browsers (MS EDGE or Internet Explorer). Open the URL with that browser which your have copied. Afterwards restart the custo diagnsotic server.
With this approach you can update the certificate store of the Apache Tomcat server of the sending pratice.
Setup of the channel to the evaluation center denied
...