How to fix Connection Lost error?

mc ver: 1.21.1//neoforge 21.1.215//modernfix 5.25.1+mc1.21.1//ATM10 ver 5.3.1 - server host is exaroton btw.. friends are able to join it.. so I don't think the issue is with the server

I have no idea how to fix this but angrily refreshing my servers multiplayer page and watching it work for friends and not me is starting to get on my nerves(some said just refreshing it sometimes works - but it hasn't worked once for me)

https://preview.redd.it/dqn5xcbm756g1.png?width=1919&format=png&auto=webp&s=1892df16f37c2a49ba7757e34f1e10feeb4dcbd9