When you type a seven-or-ten-digit phone number into an Excel cell that uses the phone number format, Excel will automatically change the way the number looks so that it appears as a phone number.

How to determine requirements in Excel Phone numbers have 10 numeric digits and generally use the (xxx) xxx-xxxx format. Let’s breakdown our requirements for a phone number: Must be 10 characters ...

If you Can't type numbers or formulas or enter data into Excel cells then it might be a problematic Add-in causing the problem. Here are some working fixes that may help.