Why does Minecraft say this:
Server forgot to send required information to construct BlockEntity
It says this when I log into certain servers in 1.10, like Mineplex or Cubecraft.
I had this exact issue today with 1.10.1
Try setting your version back to 1.10, I have had no issues with that.
If you don't know how to change your minecraft version, look here: http://gamingedus.blog.ryerson.ca/educator-minecraft-resources/minecraft-how-tos/changing-your-minecraft-game-version/
Based on this thread in the Minecraft Forums, several people are seeing this with v 1.10.1.
One of the Minecraft devs is asking people to report this error, and even mentions that they plan to release 1.10.2 later today with a fix:
I've been told that we'll have 1.10.2 later today as well, because there is a crash happening in 1.10.1 that we didn't get in testing.
In the interim, flip back to an earlier version and you should be ok.
Set your version to 1.10.2.
That was a problem of forgotting to test a part of the Minecraft code on the dev side.