OpenSprinklerGen2.git??? that’s not where the firmware is. The correct firmware is at:
https://github.com/OpenSprinkler/OpenSprinkler-Firmware
Maybe try rebooting your RPi. Also, I assume you have a fairly recent Raspbian, otherwise the issue could be due to IPv6 binding. In any case, I tried on two of my RPis and both work fine, so I can’t reproduce the issue.