Recent versions of AutoCAD change the default behavior of newly created Mtext objects. After creation you can’t change the Width in the Properties dialog! Users often want to set the width to 0.0.
For existing Mtext objects, change the Columns setting (just below the width) to “No Columns”. You will have to commit this change by pressing ESC, then reselect the Mtext to be able to change the width.
To restore previous behavior for all newly created Mtext, change the MTEXTCOLUMN to 0 in your current (and prototype) drawing.