Issue with connection attempts not working

I am new to using this software and not very knowledgeable about networking so apologies if its a simple and obvious solution.

A friend and I were trying to connect to each other via Zerotier to play a game of FlyCasual but we could not the connection to work. We are both on the same network, both nodes are authorized to be in the network and it says they are online. After some work we managed to get pings to work but still could not connect to each other.

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