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

Update: Deleted all my browsing history, cleared cache, etc. Like it was a brand new browser and now it works with no issue.

I've been hammering on the auth URL for weeks now. Testing and using the same stored token to re-authorize. Maybe stored tokens have a limit to the number of times they can be re-used?

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Having the same issue as of today. Authorization was working fine earlier - now I'm getting the same 'Matching code...' response.

Signed in and out of my Instagram account repeatedly, created a new app id and disabled/enabled Implicit Oauth - all with no success.

The 'Authorized Applications' view in my Instagram account reports that my application has indeed been authorized, but I can't make calls to the API. Authenticating through an Incognito window returned a successful response but it's not a solution.

Tried reporting to Instagram through their 'Report Issue' form, but it won't allow me to submit the form.