What is it:
Insert option under Developer tab is grayed out and not allowing you click?
Why is it disabled:
How to enable Insert button:
Once you Remove the Share Workbook option this gets enabled.
Step 1: Go to Review tab and click on Share Workbook.
Step 2: From the pop-up menu Uncheck the “Allow changes…..” option and click OK.
Step 3: Go back to Developer tab and check the Insert button, it should be enabled now.