[b]Troubleshooting Steps:[b]

1. Make sure that the cells you're trying to enter text or numbers into are not locked or protected. To check this, right-click on the cell and select "Format Cells". In the "Protection" tab, make sure that the "Locked" checkbox is unchecked. If it's checked, uncheck it and click "OK".
2. Press the "F2" key on your keyboard while the cell is selected. This will put the cell into edit mode and allow you to enter text or numbers.
3. Check if your worksheet is protected. If it is, you won't be able to enter anything into the cells. To check this, go to the "Review" tab and click on "Unprotect Sheet". If it asks for a password, you'll need to enter the password to unprotect the sheet.
4. Try closing and reopening Excel. Sometimes, Excel can get stuck and a simple restart can fix the issue.

I hope one of these solutions works for you!