Could be either, or both or something else.
Network connectivity issues could be any number of things
The version or registration state of Sublime shouldn’t make a difference
The error indicated is nothing to do with code, it’s a network/environment error
This is 6 years old theres probably much easier ways to achieve this now due to EventSub existing, likely EventSub Subscription Types | Twitch Developers is you want to consume chat messaging.
It’s not a code problem it’s a environment problem.
And from the tutorial I have no idea why the irc.connect is being cast with variables.
And if your code was working and you changed nothing and now isn’t working then the issue is environment and not code.