Airplay icon missing from iTunes on PC

My Marantz 7004 isn't even supported anymore--only had it for 3 years--and the reviews that I have read for all Marantz streaming products are all caustic.  It's really sad that a company with their resources can't do basic networking

Very disappointed with Marantz.  Should have been a lot better product / company.  Guess it's time to look around for something else and throw this thing on Craigslist or something. 

I have found a fix for this problem that I havent seen anywhere else on the internet. I hope this works for you. 

For me the icon would only show up and work every couple months, and then it would dissapear again. I was trying to connect to my Sonos speakers, which work off of other devices but not itunes... After countless hours I found the issue in my settings.

Settings > Accounts > Family & Other Devices > [Sonos] > Change from standard account to Authorized User

Good luck