you do need to use jpg as you flagged and that was an issue a few weeks ago but this issue is new.
I also tried uploading and downloading from my Google drive but then I got this error Only photo or video can be accepted as media type. (9004, OAuthException)
so this error means your cant upload to Instagram from your Google drive account - see Only photo or video can be accepted as media type. (9004, OAuthException)
I should add that carousels is working fine, just single images are not working.