How Do I Reset A Mac Application To Default Settings?

Once you suspect 'settings' are likely the fault, their location may be guessed

and the path 'Go > Go To Folder' may be used to further look into preferences.

A path to some items is harder to guess, although 'Go To Folder' is very useful.

Glad to hear that John's advice worked for you. Took me awhile to make use of

the 'Go To...' Usually because I'm not sure where to Go To. ~ While others have

suggested where I could or should go, those aren't in my Mac selections.

Good luck & happy computing! 🙂

Quit TextEdit, and drag the following folder to the Trash:

~/Library/Preferences/com.apple.TextEdit.plist

More information is required. There are thousands upon thousands of Mac apps.