BoneyToes

Hi, Newbie here. I recently purchased a 2020 Silverado RST Z71 diesel. Soon after I got it I noticed it would not go into Manual at all. I brought it back and the dealer adjusted the cable so I could get the transmission to go into M. The problem is that there still is no indent for the column shifter to settle into M. I can push the shifter to the left and it will drop into the next indent to the left. Five gears, four indents. Is there a fix?