Had my twitch username changed by twitch when I got partner and since I have had nothing but problems with nightbot, here are the steps I have personally taken to try to fix the issue.
Removed nightbot from my connections and reconnected.
Logged out and back in of my account to regrant permission.
Made nightbot part channel 4/5 times a night when it will work initially for around 10 minutes per time.
The odd thing is folk can still request songs and sometimes it will log whats going on in my channel but others it won't, besides when I initially part it from channel and have it rejoin it will not post any commands back into the channel, but if folk request songs it will add them to the actual queue.