Q: Apple TV giving "turn on home sharing" error.

For years I have had an AppleTV on each of our 3 TV's.  I have them then connect via "Computers" to my iMac which is running iTunes and has my movie library of over 2000 movies.  I've never had a problem with the "Computers" part on the AppleTV not just having all of my movies, music and TV there to pick from and watch.  However, I just moved and every since then almost every time I go to watch a movie on my computers section of the AppleTV it tells me that my Home Sharing is not on.  Which is not the case at all.  My home sharing is ALWAYS on.  And I always leave my iTunes running at all times (I learned that when I set all of this up - it won't work without iTunes being on on my iMac).  I've had this running correctly for years and now it's not working.  If I go to my iMac and unsleep it - then I have to quit iTunes and then open it again - then everything comes up.  This is very inconvenient and I know it is not the way it is meant to work.  Any advice would be GREATLY appreciated.  Thanks!

iMac (27 inch, late 2013) running OS X El Capitan Version 10.11.5

AppleTV - model A1427 Apple TV Software 7.2.1 (8011)

iTunes version 12.4.1.6