App is not working – IG Catch Video multiple Albums Review

I just purchased this app from the App Store for $2.99 & when I try to log in with my IG username & password it keeps giving me an error message that says: {"Code":403,Error_type":"OAuthForbiddenException","Error_message":"You are not a sandbox user of this client"} so basically i paid for an app that isn't working properly & I dont know how to contact the person who manages the app to let them know, hopefully they read this review. I'm sorry but I'm going to have to call apple customer service to get my $2.99 back since the app isn't working :( please let me know when this is fixed & I will re-purchase the app if I haven't found another app that offers this repost service w/o watermarks.
Review by Jeniffer Andrea on IG Catch Video multiple Albums.