I know that there is a lot of topics about that problem and I read a lot of them for 2 days but even after delete everything and start from scratch following the guide I can't link my skill...
On my server (my own) I can see the auth request with state, scope... and after the user logged in I redirect to the redirect_uri from the request with state and code as follow:
State is the one in the request from Alexa, code is a unique create from my side.
Alexa app show a waiting animation with some points then
'Unable to link .. with Alexa' 'We are experiencing a problem connecting with the skill to link your account'
For the moment the Lambda service is copy / paste from the guide and I put my skill as a trigger.
I didn't receive any token request on the server but I tested it before and it works fine.
I try from Alexa app on iPad and Android 9 and 10.
I have no log on Alexa side and no error message other than that. I don't know what to try next...