I bought a new unused Apple TV Gen 3.
That’s kind of impressive in its own way, as those have been discontinued for more than 5 years. That model could now be considered “vintage” and officially unsupported, although not officially listed there yet.
I connect it with my iPad Air2. Everytime I try to stream any content from my iPad to Apple TV I get this error "There is a problem loading this content".
What are you trying to stream from the iPad? Because that matters for compatibility.
- a file on the iPad (← may not work depending on codecs)
- an online stream from the iPad through a web browser (← may not work depending on website)
- an online stream from the iPad through a different app (← may not work depending on app/service)
- a file accessed from the iPad, when that file is located on another home networked device (← won’t work)
Use AirPlay to stream video or mirror the screen of your iPhone, iPad, or iPod touch - Apple Support
If screen mirroring or streaming isn't working on your AirPlay-compatible device - Apple Support