A short while ago, Realms disappeared! Some wondered why, and the creators told us eventually.
But, if you don’t remember why, I’ll do the honors of telling you again.
Apparently, a bug disabled Realms on their latest update at the time (I think it was the Singles Awaren–er, I mean Valentine’s Day Photo Booth update at the time, but that’s just a guess.), therefore not making it accessible. (You can also take Captain Crawfish’s word for it!)
But there’s no reason to worry now, because it’s fixed!
So if you want to continue making an unfinished whatever you’re making, or even try it out for the first time, you can! And there’s no need to worry for the Realms builders before this pesky bug – the creators have clarified that your buildings will not be gone.