I am getting a message when I open my drainage project that says "Unable to Build Network Topology for Network <network name here>" The message appears in the Microstation Message Center.
You will need to delete the network with the GEOPAK Drainage Network Delete Tool. This will prompt you to delete the network but will also give you a prompt to delete all the nodes and links which you will not delete. Just the network. Then you will create a new network with the same outlet and rebuild it and design it. It should work at that point.