Can anyone tell me why my app was working but now it doesn't work please

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I have an app that creates a room, people can connect to the room, it was working fine online with other players, but today I made a new build in unity and nobody can connect to it, when I open many apps in my computer it works I can connect multiple times, but when I send it to other people it isn't working in their PC, they can't connect and I didn't move or change anything and no errors! :neutral: