Invalid redirect error after "confirm_access"

The Community is hosting an End of Summer sweepstakes! Participants must complete tasks to earn tickets that will enter them with a chance to win a free year of Constant Contact and other great prizes!*
*No Purchase Necessary. For Official Rules, visit here. Constant Contact’s End of Summer 2020 Sweepstakes ends on October, 20, 2020 at 11:50 PM EST.

Invalid redirect error after "confirm_access"

Highlighted

Hi,

I am experiencing some problems with OAuth v2 in my ASP.Net application. After sending request to https://oauth2.constantcontact.com/oauth2/oauth/siteowner/authorize?response_type=code&client_id={my... I have been redirect to login page then confirm_access page. After I click "grant access" button, the "invalid redirect" error occurs.

I also tried the sample C# app and same error happened there too.

I have searched on forum however nothing comes cross my issue. Can you please help me troubleshooting?

Thank you!

Developer Portal

View API documentation, code samples, get your API key.

Visit Page

Constant Contact 2020 End of Summer Community Sweepstakes!

The Constant Contact User Community is hosting a sweepstakes. The more you participate, the more chances you have to win! Read on to learn more...