Vues :

Users cannot connect to DocuWare from a Mobile Client outside of their network.

Ports 80 or 443 on the Firewall may be closed for inbound/outbound traffic.

A simple test would be to try to access your DocuWare Webclient URL outside of your network.
If you cannot connect outside the network, then you will need to open port  80 or 443 (whatever may apply to your Organization) to successfully connect to Mobile Client.