UI Button is not Detecting Mouse Click

The title tells the tale.
My UI Buttons are not detecting mouse click at all.
Using unity 5.
Yes the UI Button has a canvas as a parent.
and yes it has a canvas renderer!
Im stull new to this unity visual gui stuff.
Please help!

Do you have EventSystem in your Hierarchy view? If no then you should add it, if yes then provide us screenshots with settings of EventSystem, UI Canvas and Button itself.

P.S. Okay now that finally you have provided screens - change your Canvas GraphicRaycaster BlockingMask from Nothing to either Everything or UI(or whichever layer your button is).

P.P.S. Ok, I’ve quoted my last comment over here (if you believe that to be the final answer):

Your button seems fine to me. Does it
have any visual effects? As for the
click you’ve said it to enable
queueRead - note that your button
won’t disable it afterwards (just in
case you didn’t know).

If it doesn’t get clicked at all then
there should be something in its
parents, as I see you have HUD => HUD
=> QueueReader, so far I’m only sure that you have configured the first HUD
if that was it on that screenshot
before, so check the rest or provide
their settings as well.
But still your choice of moving your button straight to main ui canvas - I’d not consider it as a solution, unless you need one of those 2 other parents to stop its child from receiving click event, and from the point to which we came it was pretty much obvious that one of those 2 causes that (that’s why moving to reconfigured main UI canvas worked).