If you experiencing problems with Excel export go through the steps below which will help you to resolve the problem. 

Please close Microsoft Excel and export again 

The problem occurs whether there is still the Excel process running in the background. The process will permanently stay open in the background unless you manually close it, or perhaps shut down/reset your PC. To manually close it, check Task manager and close all Excel processes that may run in the background. 

In case you need the Excel application running for the data analysis in the meantime of exporting the data you can toggle on the checkbox in the Dewesoft settings which enables exporting in parallel. 

Access to clipboard denied 

Excel needs also access to the clipboard for its operation. It may happen that another application is occupying the clipboard at the same time the Excel requires is. You can manually delete the clipboard in the Windows settings. 

Paste method of Worksheet class failed 

Sometimes the problems occur in regard to library limitations that Dewesoft uses for export the data to Excel format. You should try export a few times and export should pass. We are aware of the problem and we have already reported the issue to the developers of this library but haven't gotten a new version yet.