Hu that's so weird. I might update it today (If that's allowed? Idk this is my First Jam).
There should be signs that Kind of explain what you got to do. In the second room, the Green activation Stone requires the other activation Stone in the room to be active, only then it will activate and spawn the Portal for the next room.
I highly suggest to Play in fullscreen, else the Text of the signs is probably too small.
Thank you so much for playing my Game and giving Feedback though! Appreciate it :)