After Upgrading Debian from Jessie to Stretch everything works smothly, except for Icingaweb2. If I access the URL it shows me only a blank white page. Apache access.log and error.log seem normal (as far as I can see, I do not have a lot of experience with websites to be honest).
Apache Version: 2.4.25
Debian Version: 9.1
PHP Version: 7.0.19-1
IcingaWeb2 Version: 2.4.1-2.stretch
Could someone give me a tipp or help me resolve this problem?
Thx a lot