Excel is using the incorrect add-in. The BI add-ins were designed for 32-bit and 64-bit Excel and, if the 64-bit Excel is using the 32-bit add-in or vice versa, Excel will not launch the task pane.

1. Close Excel
2. Open C:\Program Files(x86)\Common Files
3. Rename BIExcelFunctions1.1 folder
4. Open Excel and click OK on the missing addin prompt(s) until you open a blank workbook
5. Go to File, Account, About Excel and confirm if your version is 32 or 64 bit
6. Go to File, Options, Add-ins
7. Click Go... button at the bottom near on Manage Excel Add-ins
8. Uncheck Sage.Bi.Excelfunctions1.1, click YES to pop up message, click OK and close Excel
9. Open C:\Program Files(x86)\Common Files
10. Rename BIExcelFunctions1.1 folder to original name (BIExcelFunctions1.1)
11. Open Excel and go to File, Options, Add ins
12. Click Go... button at the bottom near on Manage Excel Add-ins
13. Click Browse
14. Go to C:\Program Files(x86)\Common Files\BIExcelFunctions1.1 and open folder
15. Choose 32 or 64 bit folder then select Sage.BI.ExcelFunctions1.1.xll
16. In Excel Add-ins , Report Designer should be checked, click OK.
17. Go to File, Options, Add-ins and verify the following add-ins are listed in Active Application Add-ins: BI Generator, Report Designer Add-In 1.2.0, and Report Designer Add-in 1.2.0 Custom Task Pane Helper
18. Run the report again

DocLink: Missing BIgenerator and PLdrill on terminal server