Parameters windows not prompting

Dear

I have the problem that the parameter window of crystal reports isn't prompting when loading the report.

This is in Windows Server 2016 - IIS 2016. On my local machine with IIS express it works like a charm.

Reports without parameters are loading without any problem on the server. But when parameters are required I just get an empty screen (with the export, print button etc...).

Configuration: ASP.NET 4.6, Windows Server 2016, SQL Server 2017 Express.