When running this command:

/tellraw @a {
  text:"Hover.",
  hoverEvent:{
    action:show_entity,
    value:"{name:\"Bob\",type:Creeper,id:00000000-0000-0000-0000-000000000000}"
  }
}

Expected behavior:
Upon being tellraw-ed the text, it will display in chat the word "Hover." and when hovering over it, basic information about Bob the creeper will be displayed.

Actual behavior:
When I am tellraw-ed the text, the word "Hover." appears in chat, but hovering over it does nothing.

Steps to reproduce:
1. Get a command block.
2. Copy paste this command into the command block.
3. Power the command block.
4. Hover over the message.

I've tried to get this command to work - and you can see the discussion for this - over here, on github. As you can see from this discussion page, at first glance it looks to be an issue with compatibility with my environment.