Having the same issue with Pivot Table - waiting for bug to be fixed.
Is it only preview or report cannot be generated neither. as there is no monitoring tool for tasks it is difficult to say whether task was triggered an is running or it stopped with error.
I'm having this exact same issue on nPrinting 22.214.171.124. The preview hangs and throws and error with a PixelPefect report and image of a pivot table. Report is not generated as a tasks. Did you get ever get this issue resolved?
That seems to be resolved in NPrinting 17.3.0