I did the following steps:
1) Use an existing AMI with Ubuntu 16.0.
2) Create Instance from this AMI and Launch it.
3) Do nothing, just stop the instance.
4) Create AMI from this stopped instance.
Solved (using AWS Support...): Pb was due to AWS Mindterm Java SSH Browser which cannot connect to this instance.
But using Putty works well, "Other Linux" does not have influence.
1.) Other Linux means No vanilla Ubuntu (default Ubuntu changed). 2.) Can be connect to EC VM using Putty putty -ssh loginName@Ipadress Dont forget to convert PEM file to PPK using PuttyGen 1st. login depends on the original AMI instance, here ubuntu/root can be used since this is Ubuntu Amazon.
Compare to google Cloud, AWS does not have robust Web Browser SSH, so 3rd party SSH is needed.