Hello
As per the directions you deleted in order to post this… I fixed your posted code formatting
This is not really a code fixit shop but have you tested those motor commands without Blynk… say using a loop or physical button to process a similar type of function?
Do you even have the Motor Shield configured properly???
And how can you use the same pins for two serial devices?
I think your issues are totally non-Blynk related… get it working without Blynk first, then add in the Blynk control of the tested and working functions.