I do have the right to post my iMovie project to Instagram using iTunes music for the movie

If by 'iTunes Music' you mean songs or other music you have purchased from the iTunes Store, these are copyrighted and you have no right to use them in your project: indeed doing so could lay you open to legal action and substantial damages.

Being allowed to use a song in an iMovie that you have on your computer for your own personal use is different than creating a movie and posting in on Instagram. That is definitely not covered in the license you have for the music. You would have to request permission from, in this case, INXS to use the music. There would most likely be a fee.

iMovie is assessing the music purely on a technical level - for example, if an item is only in the 'cloud' you can't use it without downloading it. It can't detect whether you would be breaching copyright.

You're missing the point here. Your argument is not with iTunes or iMovie. It's with Instagram. Even if you believe and can convince everyone here that you have the right to the song, it's not us you have to convince... it's them.

I’m having a hard time posting to Instagram without going through having to then repost Answering to their agreement that I do have the right to post

So, your question has nothing to do with iTunes, it's with Instagram. Now, that wasn't too difficult for you was it?

allentodd wrote:

No I wasn’t missing the point. It was the other guy failing to give a simple straight up answer.

The images in your original post make it quite clear that Instagram is rejecting your submission because they suspect it contains copyrighted material: and as I explained songs you purchased in iTunes are copyright and cannot be used without a written permission (which you are not likely to get). iMove will reject songs with DRM (protection) but iTunes songs are no longer sold with this - that doesn't mean that they are free to use. Instragram is very properly requiring that you provide proof of permission to use this material, which you evidently haven't got. If you cannot get written permission you will have to remove the music. That's as straight up as I can make it.