Excel puzzle - can't type into cell, exhausted support steps, need a tech wizard !

Typing fails in both the grid and formula bar even in a new workbook, while Excel’s search box and other Mac apps accept input. That rules out worksheet protection or a dead keyboard. Use Help > Check for Updates and install the newest Excel build, then compare the symptom with Microsoft’s Excel for Mac known-issues page. Quit Excel and temporarily disable Excel add-ins through Tools > Excel Add-ins; also remove any files from Excel’s startup folders, then relaunch. Holding Shift while opening Excel should not be treated as an add-in isolation test on macOS. Test Excel in a new user account. If typing works there, the cause is in the original user’s Excel preferences, startup content, or permissions, which reinstalling Office may leave behind. If it fails in the new account, capture a screen recording, Excel version, macOS build, input-source layout, and installed add-ins, then use Help > Contact Support.