My text formatting disappeared
If you suddenly lost all text formatting in a TextEdit document, you may have accidentally converted your file from rich text to plain text format. Plain text documents cannot be formatted.
To restore formatting, you can try reverting the document. The document will be as it was when you last saved it.
You can also change the document back to Rich Text and add formatting; however, any previous formatting will be lost.
To restore the document back to the last saved version, choose File > "Revert to Saved."
To convert the file to an RTF, choose Format > Make Rich Text.