You probably are not saving it after you change it. I hit edit, then changed prefix to solved, then hit save at the bottom of the text box and it worked.I can't get my Thread prefix to change from Unidentified to Solved. I just did it not too long ago . Now I can't change it.
I can't get my Thread prefix to change from Unidentified to Solved. I just did it not too long ago . Now I can't change it.