phpinfo.php error 503 service not available ispconfig3 ubuntu16 on second level domain

Ahoi all,
after Iget the older php versions (via ppa repo installed) on ubuntu server 16.04 and latest ispconfig stable running Im not able to run phpinfo.php with a second level domain with own IP.
I want to install ex. owncloud so I create a site own.test.xyz.
I enabled php5.6-fpm and access the phpinfo.php getting error 503 service unavailable.
phpinfo is accessible on test.xyz with different php (5.5, 5.6, 7.0)versions.
Could not find errors in apache, php-fpm.log or syslog.

Can someone help?
Tia
Stefan