I managed through the below

If the Task Pane doesn't show in Excel do the following:

1. In Excel,  click the Microsoft Ball at the top left corner
2. Click Excel Options
3. Click Add-Ins
4. At the bottom of the window, in the  Manage section, select Excel Add-ins click Go button
5. Click Browse
6. Browse to  C:\Program Files(x86)\Common Files\BIExcelFunctions\32bit\Sage.BI.ExcelFunctions.xll
7. • Note:That will add Report Designer Add-In 1.0.0
8. Select  Report Designer Add-In 1.0.0 check box and click Ok
9. • Report Designer Add-In 1.0.0 should now be listed under the Active Add-ins section
10. Close window
11. If the Task Pane still does not show, click Add-In tab from the Office Ribbon
12. Under Report Designer Add-In  select Show Task Pane which can be used to unhide/hide the Task Panes that you will see to the right of Excel Reports
13. Run the  Report Designer Add-in 1.0.0  report

Office 365 is not supported or compatible with Report Designer. It must be a local installation of Excel.