"Error validating verification code. Please make sure your redirect_uri is identical to the one you (truncated...)

I'm using Laravel/Socialite to generate a login for Facebook OAuth.

That URL is <my domain>/auth/facebook?appUser=a@b.com

As a means of "stabbing in the dark" i've added the following Auth redirect URIs into the Facebook app:

http://<my domain>/auth/facebook/callback

http://<my domain>/auth/facebook/callback/

http://<my domain>/auth/facebook/callback?appUser

http://<my domain>/auth/facebook/callback?appUser=%3F

http://<my domain>/auth/facebook/callback?appUser=%2F

http://<my domain>/auth/facebook/callback?appUser=%3F%2F

But once the Facebook login happens, i'm redirected to:

http://<my domain>/auth/facebook/callback?appUser=a%40b.co.uk&code=<code>

and the above URL then generates an error of Error validating verification code. Please make sure your redirect_uri is identical to the one you (truncated...)

I have tried urlencodeing my domain, the parameters in the URL, the value of the parameter in the URL but no no avail.

Can somebody offer some advice here please?

via Chebli Mohamed