Use the .NET Framework Repair Tool

1. Download .NET Framework Repair Tool: https://support.microsoft.com/en-us/help/2698555/microsoft-net-framework-repair-tool-is-available
2. Select the files to download and click Next:
   
3. Run the NetFxRepairTool.exe file. If you've read and accept the license terms, check the I have read and accept the license terms box. Click Next.
   
4. You will see changes the tool recommends making. Click Next to apply the changes:
   
5. When the changes are made, do not click Finish but click Next:
   
6. On the final step, click Finish:
   
7. Restart your machine.

Related issues

No Ablebits tabs in the Excel ribbon
Ablebits tabs are present but not clickable
Excel crashes when you use Ultimate Suite

See also

Ultimate Suite troubleshooting