It seems that Twitter is not getting on too well with other social networks including Instagram. So now if you post on Instagram and use the direct link to Twitter to post there too your picture is no longer shown natively on Twitter (this appears to be happening with YouTube too).
If native photo posting to Twitter is important to you I have some IFTTT recipes to help. This is a two part arrangement that requires a Dropbox account. Part 1 downloads your Instagram photo to a specific folder in Dropbox using the caption as the filename. Part 2 is triggered by a new file upload in that Dropbox folder, it uploads the file to Twitter natively. The file name (which was the Instagram caption) is used as the tweet text.
Please note that there are no spaces in the tweet text as this process replaces spaces with underscores. I hope this doesn’t prove too troublesome for you.
The recipes you need are below.
Here’s example output from Twitter:
— Dan Wilson (@nadnosliw) September 24, 2015
Add both of these recipes and you’re good to go. Please note that if you want to use a different folder in Dropbox you must update the file path accordingly in both recipes.