Hmm yeah, might be something on your end blocking it - I copied your code on my end and it worked after the changes I mentioned above (even before it never broke on the tcpClient connection.)
This is the IrcClient.cs I have now, but I’ve only changed what I mentioned above.
I would suggest checking out another existing IRC library to see if that one works as intended - I can’t think of anything at the moment of what else could block it on your end.