2 php version get 502 error

[r_ekkie]

Today I started with migrating the first clients from PHP 5.4 to 7.0
PHP5.4 is installed with mod_php and 7.0 with php_fpm.
server is running CenOS 6.5 with Directadmin and Custombuild 2.0

First did a test wit my own domain. that works with out any problem.

Now I tried to migrate the first client and I get the following error:

Proxy Error

The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /index.php.

Reason: DNS lookup failure for: php-fpm70.username


Additionally, a 502 Bad Gateway error was encountered while trying to use an ErrorDocument to handle the request.

what did I forget to do?

Thanks