Backdrop: You are running a setup involving the Enterprise Portal (EP) & Knowledge Management (KM).
Details: You have recently upgraded the Enterprise Portal e.g. from 7.00 to 7.3 or 7.3 to 74 and have performed a delta copy of the content currently maintained within the Collaboration Rooms (older version).
After performing this action you noticed that the "Room Structures" i.e. the general room makeup markers have indeed been transported correctly however the Room contents have not been carried over 
What are we dealing with here: Essentially here in this instance you have managed to transport and bring in the previously utilized Collaboration Room setup into the newer Portal Version although the Rooms themselves are blank and missing the core content required for business operations.
Question:
What content KM Content do you need to export from the old system to the new system so the collaboration rooms are displayed correctly?
Answer:
All content located in the collaboration rooms is stored in the 'room_extensions' repository. You should transport the content of this repository if you wish to make the same available in the destination system.
Select Content Administration - KM Content • Navigate to folder path /root/room_extensions 
Core Guidance Points
- Transporting Templates: https://help.sap.com/saphelp_nw73/helpdata/en/e3/d9f74122c9c417e10000000a155106/content.htm
For a reference overview a similar overview is also provided in Transport of Collaboration Room Templates: https://scn.sap.com/thread/495322
ICE
The KM ICE Distribution guide is accessible via the link below therefore the first recommendation would be to ensure the process is being followed carefully:
There is also an additional guidance document available below for additional reference purposes "Getting Started with ICE":