You aren't accounting for your header row:
Time,GVPos,VlvLimCmd,SpeedCtrlSP,Speed,PIDOut
"Time" is clearly not in the datetime format.
Assuming you've handled that separately, your first column is NOT in the correct format:
12:38:06.865,6.021393,8,102.5,102.412323,6.069856
That is clearly a period "." not a semicolon ";" between seconds and fractional seconds.
Thank you for posting your actual code (and not a billion lines of useless fluff around it), as well as your actual test data. This makes for an amazingly simple and unambiguous question, and makes it extremely easy and desirable for us to want to help you.
