About half the time I schedule FB and IG posts, they work in unison. The other half is where I get the message in my email, "Sorry, we couldn't publish on Instagram."

Then it says that it did publish on Facebook. Why does this error happen for IG when there isn't a disconnect happening with the account? It's as if IG doesn't like Zoho or something.

It's frustrating to schedule posts and then get denied. Could it be the size of the graphic? What are the dimensions and MB max? I always post a graphic of1080x1080 px with a max of about 1.2MB. 

Please advise what could be causing this problem with IG and never with FB. Thank you.