A lot of users of the MIUI ROM on Xiaomi phones and otherwise experienced a severe bug when trying to use Instagram.
The bug meant that only a pitch black picture got uploaded, dismissing your meticulous detail that went into framing the picture. At first, it was believed to be a bug present only on the Mi 4 but it was later confirmed that it exists on all phones running MIUI.
The latest update though solves the issue, and pictures on your Instagram are back to being the awesome they’re meant to be. If you haven’t received the update, it could be because it is meant for users on the beta channel of MIUI, which receives a weekly OTA update.
Such bugs are really uncalled for, but fortunately Xiaomi has a decent update system in place which often means that bugs and errors are taken care of in due time.