I had this happen on an El Capitan system where httpd was previously working fine.
I suspect that the 10.11.4 OS update removed that option from Apache, since I applied the update just before the problem, but there's no mention of this change in Apple's documentation: About the security content of OS X El Capitan v10.11.4 and Security Update 2016-002 - Apple Support
Thank you for your post.
First, FileMaker Server 14.0.4 is the first version to run under Mac OS X 10.11.x (El Capitan). Please see Knowledge Base Article #15364 for complete information.
Next, install the FileMaker Server 14.0.4b update via Knowledge Base Article #15575:
Let me know if you run into any issues with the update.