There’s also an alternative way to disable the Compatibility mode in Excel. Here’s how! Go to File Menu > Info. Then, hit the Check for issues drop-down button under Inspect Workbook heading.

Menu options being grayed out in Microsoft Excel is quite common. Some menu options go grayed or unavailable when editing a cell in your worksheet ... from that, compatibility issues with Excel ...

Excel allows you to lock specific areas of a sheet with a password or protect ... they aren't foolproof and may cause compatibility issues with some third-party applications.