The connection issue is a specific Incident report, so we have to focus on connectivity issues, analyzing the entire end-to-end from the reporting User's network to the PBX's one.
We start from the User's network. First we have to check the client connection status. In any case we force a App - Force Manual Reconnection, so we are sure that the connection action is correctly triggered and thus we can collect answer by the client. If the connection proceeds fine, then the User experienced a Temporary Network Problem which is now over and then the Incident is closed, otherwise we write the exact error message (if any) about the connection problem. Using this message we App - Check the Configuration of the Application of the application, looking for misconfigurations which might lead to the incident reported. Example Given: pbx wrong address or port.
If the Configuration of the Application is somehow wrong, we Fix The Configuration and test if the User can connect to the PrivateServer correctly. If the connection works fine, then we close the Incident.
If the configuration looks fine but the Application continue to complain about connecting, then we can move the checks on the Server side. First we need to understand if the User's account is actually present on the PrivateServer. If it's not, then we have to create the User Account or verify why this mismatch is in progress. Either ways lead us to closing the Incident.
If the User is present, but still the Application can't connect, then we need to investigate if some of the account settings differs from the one on the Application. Our main suspect here is the password, so we check if there's a password mismatch and possibly change it to get it along with the one set up in the Application.
If even this step doesn't help identifying the cause of the incident or doesn't close the incident, then we need to escalate.
The second level is in charge to fully evaluate the server configuration to understand if the connection problem is somehow related to some issues on the server.
First thing to do is to check the Network, as the connection problem is mostly network driven. If the check goes fine, then we check the server services, paying particular attention to the Asterisk server and to the Database backend, as they are potentially to blame for such behavior.
If the services are fine, we must investigate further what's really happening and so we go down into the client logs. If nothing arise from there, we can just escalate to the third level.