Hi Judith,
Thank you for posting your question in this community. It sounds like your Excel workbook is enabled “Protect workbook”. If the workbook is protected, “Delete Sheet” will be grayed out, but the reset will not be grayed out.
In this scenario, you need to go to Review tab > Protect group to unprotect the workbook.
For your information:
If the problem still exists, may I know the following information at your convenience?
1: Does the problem happen in all your Excel workbooks or this particular workbook?
2: You can try to create a new blank workbook and see whether the same scenario occurred.
3: Does this workbook contain any VBA code since we can also use VBA to protect workbook from certain actions?
Best regards,
Dihao