Could you post the complete error from your console? You could edit your question and copy paste it into there.
I do not receive more informatie on the screen only.
An error has occurred while handling the request.
After starting the app view in Import_OverView then error accurs.
New Edit Import file Delete ▲ Filename Template nr Template name Consolidatie-01-01-2000-31-12-2199.xls 9 BewaardersTelefoon
If you are doing this in the cloud, you can go to the app platform and view the most recent log file, which will have a lot of detail about what caused the error. It will be 50 or 100 lines of information depending on what the error is.
If you are doing this in the modeler, as Ronald indicated, the error will show up in the Console tab at the bottom center of the Modeler window. In this case, you'll see one or two error lines, and double-clicking on one of them will show the detailed error information produced (50 or 100 lines).
Hope that helps,