Cannot summon armour stands

Put the summary of the bug you're having here

What I expected to happen was
That i could Summon an Armour stand

What actually happened was
That the chat said:"unable to summon object"

Steps to Reproduce:
1. Get a command block by typing: /Give <Player name> minecraft:command_block
2. Place the command block
3. type in the command block "summon ArmorStand"
Or
1. Type in the chat "/summon Armorstand"