Deathstryker

I get to the point where the tutorial wants me to destroy the 3 targets using HE rounds (which I was unable to switch to with the "R" key. Had to use the action menu). After I destroyed these targets, the tutorial asked me to switch to the machine gun with the "F" key which I did however the dialog prompting me to do so remains and the tank just sits there at the top of the hill. Am I doing something wrong? I've tried this mission twice now. I used the search function and could not find this issue, strangely enough.