Could you try via "Copy to Instagram" instead ? It looks like that the most recent Instagram update introduced an issue - Guido/ Lr Mobile QE
I don't see copy to instagram option. I tried open in instagram but still not working.
I have had exactly the same issue-since updating to IOS14 on both an iPhone and iPad the "copy to Instagram" option (which was the only one that worked - the "Instagram" one didn't) has vanished!
Hoping for LR fix
I have the exact same issue. My Copy to Instagram option is gone and the Instagram option is completely broken. I've been saving to photos and uploading from there.
Latest instagram update partially fixed issue. You can now share directly again but less functionality.