I use Kodi/libreelec nightly builds on a raspberry pi3, they had a recent change that required a user/password be set for the web server, I believe it began on (or around) the #0519 build. Upon boot, I was required to enter a user/pass for the Web Server: Settings > Control > Web Server Username & Password.
I didn’t think much of it, but later (days) noticed that Yatse still controlled the device, but showed offline.
I went back and forward a few builds, and the “offline” problem remained I guess because the user/pass was saved, but I forgot about that new required setting. Today I went through the Yatse Help>Common Problems (Knowledge Base) > FAQ > Kodi Issues and Solutions > My host is always shown as offline
It does mention the web server, but with the new Kodi change, it would have been helpful to me if the FAQ had specifically mentioned to check the username/password fields, and then how to change those on the existing Yatse host. I created a new host first, then figured out how to edit the existing one. I was looking in the settings menu to change the user/pass, but that isn’t where it’s located. Had I not created a new host, I never would have found it.