Alexa Skills: unable to link home assistant with alexa

Configuration
1

I have my HA running on duckdns and able to integrate google assistant. Now I am trying in Alexa, when I link the account in the app it says " unable to link home assistant with alexa".

I read on the forum about port forwarding, I am already working with port 8123. So dont know what to edit.

I did the test in Lambda function and it worked.

in HA I have this error:

Login attempt or request with invalid authentication from ec2-54-74-32-16.eu-west-1.compute.amazonaws.com (54.74.32.16). See the log for details.

2

I am newibiee but i just followed each instructions step by step and its working perfectly for me.

3

I almost did it.

followed this:

4

How did u solved this?