If one of your latest Instagram posts is not appearing under the sync section, there might be a few reasons:
Instagram is having a delay on their BASIC APIs
The post is a Collaboration post which is not supported by Instagram APIs
In both cases, the solution is to switch to the Instagram Graph APIs, which are only available for Business/Creator accounts.
To do so, follow these simple steps:
Disconnect from your current connection, by clicking the Disconnect button at the top of the sync page.
Connect again, but this time use the second Connect button, the one at the bottom of the page that says Connect via FB Business instead
