prefabs and materials not working on another system

Our problem seems like rare, as I did research and none find to answer my question.

The problem is, I have created prefabs ,materials on my system and then exported it to my partner's System.

Now when my partner import it on his system all prefabs and materials I created showing "white" icon (not gray)

When we try to drag it to scene its not working.

Does anyone know answer to it?