LCD 20x4 ( 4 bits ) lib

//LCD.c
void lcd_delay(int msec) {
        volatile uint32_t done = msTicks + msec;
        while (msTicks != done)
                ;
}

//LCD.h
volatile uint32_t msTicks;
//...

//VTABLE.c
void SysTick_Handler(void) {
        msTicks++;
}

//LCD.c
void lcd_delay(int msec) {
        volatile uint32_t done = msTicks + msec;
        while (msTicks != done)
                ;
}

//LCD.h
volatile uint32_t msTicks;
//...

//VTABLE.c
void SysTick_Handler(void) {
        msTicks++;
}

So it would make sense to check whether you're actually executing SysTick_Handler.