You have to use an AI Script to turn on shared vision. It dosen't happen automatically when you set alliance status.
Example: You want Player 1 to have vision for Player 7. You use this trigger:
Trigger |
Players: |
¤ Player 1 |
Conditions: |
¤ Always. |
Actions: |
¤ Execute AI script 'Turn ON Shared Vision for Player 7'. |