Firmware written in Flash but program is not working?

i’m trying to upload my code to mts_dragonfly_f411re . Even after successful upload, the code does not work. I have used the simple code of led blink:

#include "mbed.h"
DigitalOut myled(D3);
int main() {
while(1) {
myled = 1;
myled = 0;

This works perfectly with bin file made from mbed-cli and mbed online compiler.
How can I fix this problem?

Please file an issue here Issues · platformio/platform-ststm32 · GitHub

Ok, I have posted the issue there.