Not sure I understand fully but anyway:
Questions:
1. Are you using the CnCNet client from here: https://cncnet.org/red-alert-2
2. Are you using the LAN option in the CNCNet client, or in game?
3. If you can't see anyone in the LAN lobby of the CnCNet client, it could be a network sharing issue, e.g. your PC or others not allowing to be seen on the network.
Alternatively, have you tried just using CnCNet online option instead of LAN. Would allow all of you to be online and have the benefits of custom map transfers etc.