Instagram does not accept Rush export clip

Hi there,

In recent weeks, I found the video exported from Rush are not accepted by IG when I tried to upload them.
I tried different resolution and frame rate settings, still the same.
IG loaded my video for preview, tagging and even let me compose the caption, but at the very last step - the video won't publish. It just stated 'the video can't be shared' and does not explain why.

Does anyone has the same issue? The same video is fine for upload on YouTube, Twitter etc. so it is clearly issues with IG??