Instagram returning “Matching code was not found or was already used” when using OAuth

Question

I am trying to use the Instagram OAuth using the developer documentation at

https://www.instagram.com/developer/authentication/.

Step 1 and 2 a

Answer 1

We're experiencing the same issue since yesterday (after months of working fine) - have reported it as an issue yesterday via the 'Report Issue' function on https://www.instagram.com/developer/clients/manage/ and I'd encourage you to do the same.

Yet to hear back, but seems likely it's their end having issues rather than something we're doing.

EDIT: It's also working fine for us on our development servers (which use different IPs for interacting with IG's API) but not working on our production server from any of the IPs we have available on the production server.

EDIT2: (July 2016) Just tested and it's mysteriously started working again on our production servers. No reply to the support ticket from Instagram as yet.

EDIT3: (December 2016) And now it's failing again with the same message... Seems like it's Instagram's end again. Nothing much we can do. Frustrating.