Adobe Illustrator Operation Cannot Complete Because Of An Unknown Error Parm 90%

Adobe Illustrator's "The operation cannot complete because of an unknown error (PARM)"

Close Illustrator, then relaunch it while immediately holding Cmd+Option+Shift (Mac) or Ctrl+Alt+Shift (Windows). testing after each step.

If you get the error while resizing a text box, try expanding the box manually to reveal hidden text before performing other edits. testing after each step.

Try the following methods in order, testing after each step. testing after each step.