No text or data showing in my cells....

Please answer these questions:

• Windows or Mac?
• Excel desktop app or Excel on the web?
• Does the text appear in the Formula Bar while you're typing, or is it blank there too?
• Does this happen in every workbook or only one file?
• Can you paste data into a cell, or does that also fail?

Excel accepts navigation but is not displaying what you enter, so first determine whether the values exist but are hidden. Type a value, select that cell, and check the formula bar. If the value appears there, select the range and choose Home > Clear > Clear Formats, then set Font Color to Automatic and Number Format to General. Also check that row height and column width are not zero. If the formula bar is blank too, create a blank workbook and test there. A workbook-only failure points to sheet protection, formatting, or corruption; an all-workbook failure points to Excel itself. On Windows, press Windows+R, run excel /safe, and test again. If Safe Mode works, disable Excel and COM add-ins one at a time. If it still fails, update Microsoft 365 and run an Online Repair. Before repairing, save a copy of the affected workbook so formatting changes can be reversed.

First, type a value into a cell and look at the formula bar above the worksheet. If the value appears there but not in the cell, the data was entered and the problem is formatting. Select the affected cells, set the font color to Automatic or Black, change the number format to General, then use Home > Clear > Clear Formats.
If nothing appears in either the cell or the formula bar, check whether the sheet is protected under Review > Unprotect Sheet. Also test in a new blank workbook. If the same problem happens there, close and reopen Excel; if it continues, start Excel in Safe Mode to check whether an add-in is interfering.