Alexa, unable to link smart home skill

I am trying to link my smart home skill to my OAuth 2.0 server.

The error happens when I redirect the Access Token request to:

https://pitangui.amazon.com/api/skill/link/XXXXXXXXXXXXXX?access_token=b6bcd5a1870322898864d1a5284af5abac58d619&state=xyz&token_type=Bearer

I also tried:

https://pitangui.amazon.com/api/skill/link/XXXXXXXXXXXXXX#access_token=b6bcd5a1870322898864d1a5284af5abac58d619&state=xyz&token_type=Bearer

But the erros persist.

Anyone know what I'm doing wrong?