I found the problem. and solved.
in discourse-setup shell script at line 281
sed -i -e "s/^ #LETSENCRYPT_ACCOUNT_EMAIL: your.email@example.com/ LETSENCRYPT_ACCOUNT_EMAIL: $letsencrypt_account_email/w $changelog" $config_file
you have to replace your.email@example.com with me@example.com and after that the script works