If your A:drive is a mapped drive, then this is not supported.
See the following for NPrinting supported configuration information
Keep your NPrinting templates on an accessible local or network drive that is not a mapped drive.
Ensure that you do not have the template open in the desktop when you attempt to edit it.
Try to also create a new template as this one may have become corrupted.
If you still experience issue, please submit a support request to the Qlik Support desk directly so that your technical support issues can be investigated in detail.
I faced the same issue recently, and after little research and experimentation, I can state that the problem lays in Excel Slicers. After removing them from template, it works pretty fine. If you still need Slicers in final Excel report, you may write VBA-code which creates them (using Record Macros functionality, for instance), and set Workbook-Open trigger on it. The result would be as follows: user opens the report, macros starts instantly and creates the desired Slicers dynamically.