When I run a freshly cloned version of this program to train connect4, all graphs in the Total_reward-section of tensorboard become flat lines (Total reward=10, Mean value=0, Episode length=11, MuZero reward=0, Opponent reward=0). The graphs in all of the other sections look ok I think. I get this result both locally and in Google colab.

It worked before 91afb1d so maybe something broke there?