Recently we begun to receive this response.
Error:
code:400
error_message: "The access_token provided is invalid."
error_type:"OAuthAccessTokenException"
Checking in Instagram documentation seems that the endpoint used by your module should be this one: https://www.instagram.com/developer/endpoints/users/#get_users
If it's that it could be something with the scope?
I really have no idea where to start as this module (and the code that use it) was written by an ex-colleague.