Keyboard arrows will not move cursor
Please check if you have enabled Scroll Lock (check its keyboard indicator, and press relevant key).
Mike Thank you but that was not the problem
Sometimes other subwindows, or toolbars get the focus. Pressing F6 a few times¹ will return the cursor to the spreadsheet.
¹ At most seven times, if two toolbars are shown; one more time for each toolbar, one for the Navigator, etc.
EDIT: “Press Ctrl+F6 to switch to the document.” Source: Activating menu bar, toolbars, windows, and document.
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