We are moving a site for a customer to a new server. The customer is not interested in spending time on upgrading the concrete site to a newer version.
When we try to move it to our new Plesk Onyx server where we have installed PHP5.6 it fails with a white screen. There are no errors in the serverlogs and no errors are displayed in php. We have activated concrete5 debug mode and display errors on the server. We have tried different php handlers, but no luck.

Anyone have any pointers on where to start looking for incompatibility?

We have only added Deluxe Image Gallery 1.6.2 addon.

I look forward to any suggestions.

Best regards.