AMP causes 404 Errors

If you go to my site http://www.mastercrafthomeimprovement.com/ and look at the source code, you will see an html line
<link rel=”amphtml” href=”http://www.mastercrafthomeimprovement.com/amp/” />

When I turn off the AMP plugin, the code goes away so I assume this comes from the AMP plugin. If you check out http://www.mastercrafthomeimprovement.com/amp/ you will find that it links to a 404 page. How do I fix this?