Invalid CSRF token.

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I am trying to Create an Application Integration however I keep getting error message.


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Hello KamyarF3,


Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.


It looks like you were able to successfully generate a V3 API key within the account you are posting from, so you may have already resolved your issue. 


However, if you were trying to use the key you had generated to connect a 3rd party developed integration and at that point were receiving the error, please feel free to let us know more details about the integration you were trying to connect.


You can contact our team directly at and reference case #30875001 to let us know more details regarding at which point in the process you are receiving the error and whether you are trying to connect a 3rd party integration or planning on developing your own so that we can better assist with pinpointing the root cause of the issue.


Please have a look and let us know if you have any other questions!


Courtney E.
Tier II API Support Engineer

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If so, please mark my post as an "Accepted Solution" by clicking the Accept as Solution button in the bottom right hand corner of this post.
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How did you know he solved the issue ?

i still face the same challenge 

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Also same problem. How to solve?

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I ended up deleting the app and rebuilding it.  This was to connect MailOptin to Constant Contact.  I added the API key and secret key and then added the recommended Redirect URI from the plugin, THEN hit Save. Then back in MailOption I pressed the authorize button.  

I think if you do it out of sequence or try to authorize before you have the Redirect URI you will get this error.

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