Select the “Review” Ribbon Form the Top of Your Excel Sheet
Select the “Check Accessibility” Button
On the Right Side the Results will Come in
When You Select Any of the Results It Will Bring You to The Issue
When selecting one of the selected issues it brings you to the selected issue.
The issue here is that there are merged cells which makes it harder for a screen reader to read this would go against the best practices for making an excel sheet. You can find more information about this with the following article How to Use Best Practices When Creating an Excel with Accessibility in Mind
Some of the issues might include some of the formatting that is included in the How to Add Alternative Text to Excel (Desktop Mac) or missing alterative text which can be found How to Add Alternative Text to Excel (Desktop Mac).