Automatic Wi-fi sync of iPhone/iPad has stopped working

Recently I have noticed that the auto sync of my iPhone and iPad has stopped working. I first discovered this a couple weeks ago when I would update an app in iTunes or on my device and it wouldn't show up on the other. I cut the cord several months ago and use Wi-Fi sync and iCloud backup. As such, I just take things for granted since everything worked perfectly. Upon checking the settings for Wi-Fi sync on my devices I immediately noticed several days had gone by since the last sync had been performed.

This software on my iPad and iPhone are up to date and I am running version 11 of iTunes.

Techinacly this is not a problem because if I push the Sync button in iTunes or Sync Now on my iPhone or iPad the sync begins immediately over Wi-fi.

To summarize, when my iPhone or iPad are plugged into power they do not sync automatically as Apple's knowledgebase states. However, if I push the manual buttons in iTunes or on the devices syncing begins immediately.

I should add that I can't pinpoint when this began but it's around the time of the new version 11 of iTunes. I also changed the syncing of my iPhone and iPad to a new computer but do not see how that should be an issue as everything else works perfectly such as the iCloud backup.

(My computer is up and running with iTunes open and my iPhone and iPad I plugged in to an auxiliary power source)