Facebook OAuthException: The access token could not be decrypted

Question

I have a running application that does scheduled wall posts to one of their friends on behalf of the user.

The application was running fine for quite some time but recently quiet a few of the users have reported the messages not being posted.

The logs shows

OAuthException: The access token could not be decrypted. 

Even if the user revisits the application and resets their Access token the exception persists.

What may be the root of the error and ways to work around it?

Answer 1

If you get the following error message when making HTTP requests to the Facebook API:

{
  "error": {
       "message": "The access token could not be decrypted",
       "type": "OAuthException",
       "code": 190
  }
}

it means that the access token you are sending to Facebook when you make the HTTP request is NOT valid.

If you look at the HTTP response headers you will see a field like this:

WWW-Authenticate:OAuth "Facebook Platform" "invalid_token" "The access token could not be decrypted"

I was receiving the error above because I was sending an access token that was 1 character shorter than what was the valid one.
After comparing the access token persisted with the one I was sending I discovered this mistake.

You can check the validity of the OAuth 2.0 access token (bearer token) used on Facebook with the Access Token Debugger.