A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Try this
Tap the triangle in the upper-left corner of the worksheet. This selects the entire sheet.
Tap Home. Look for Cell Format / Format on the ribbon.
Choose Hide & Unhide > Unhide Rows.
Repeat and choose Unhide Columns.
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One additional possibility on iPad is Sheet View. Excel for mobile can put row/column hiding into a Sheet View rather than changing the default worksheet view. If the above doesn’t work, check View > Sheet View and switch back to the default view.