Authorizing new connections to Instagram is currently not possible on the IFTTT mobile apps
Incident Report for IFTTT
This issue is now resolved and you should be able to connect to Instagram on the mobile apps without problems.
Posted 12 months ago. Mar 12, 2018 - 10:49 PDT
There is currently an issue preventing users from making new connections to the Instagram service on the mobile apps. While this is being fixed, please connect to Instagram via on a laptop or desktop. If you already have connected to Instagram, you shouldn't experience any problems.
Posted 12 months ago. Mar 06, 2018 - 15:18 PST