Xcode 8.3.3 autolayout - view is disappearing runtime when setting constraints

I'm trying to make a divider, so what I do is:

1) Make a new View

2) Change the background to the color I want the divider to be

3) Control click and center it horizontally on a label on top of it

4) Compile, my view is gone.

5) Remove constraints, compile, my view is there.

6) Add left and right constraint for autosize, compile, view is gone.

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It also states that the height of my view is ambiguous.

How can the view be gone by merely constraining it?

Screenshot:

here is my output I tried in swift using Xcode and tried setting constraints as I do