They need to deploy the solution with "Cloud Onboarding" completed, enabling Apple Push Notifications. The socket-type connectivity is no longer supported. The link in the post above describes that process. When the network the device is on changes, due to VPN, moving from Wi-Fi to LTE, etc, the application will need to be able to connect from its new address/interface. If your organization hasn't deployed the collaboration edge, then the software will not be able to reach the infrastructure from outside the corporate network, without a VPN connection. You would receive a push/toast but the software won't function as it cannot connect.
If this was deployed internally as an air-gapped sort of solution then I suppose this is how it works. The application will be suspended, and then it will not be aware that anything has happened since it cannot be woken up. The thread is rather old, and the push notifications were not always an option. It's possible the deployed solution isn't up-to-date to support that capability, or that it hasn't been turned on if it is mostly in maintenance without someone researching and setting up new features.
As an end user you can't fix this, I would tell your IT support staffs that Jabber suspends and you aren't getting the push notifications to wake it up.
PS: One other point on iPhones is to make sure not to disable notifications in Settings, or you won't know something is going on either.
