Your image was really hard to read, but I could barely make out this is Rizon, and the host behind the round-robin pool is disconnecting.
Is this happening at other networks like Libera.Chat or just this 1? If it's just this 1, there's a chance they banned you. If it's only the 1 network, you can try their webchat to see if they can tell if they've intentionally blocked you for some reason: https://rizon.net/chat
Another cause might be if you went into options/connect/options/ports then checked an option to prioritize ipv6 and you don't have that.
If there's some kind of problem with your firewall that you don't realize, one test could be to install mirc again into a new folder like c:\mirc\ then see if it works from there. If it does, then either you have a setting in the old mirc that's causing problems, or there really is something that made your firewall not like the old setup.
But the best bet would be to try to connect to a different network and see if there's an mirc channel there that can help, such as EFnet Libera.Chat Swiftirc