Error Transmitting data via UART when using ADC & DMA (works separately)

Hi All,

I have been a little confused about my code and would appreciate some help greatly...

I have a basic program where I would like to read the ADC values from a sensor, and transmit them via UART for later signal processing and whatnot.

The structure is simple, and when I tested out reading the values from the ADC, as well as sending strings via UART - they both work perfectly fine. But now when I merge the two, the UART does not work anymore... I do not see anything in my serial monitor (Putty)

I feel like I am missing something big, but cannot find it. I would appreciate it if someone pointed me in the right direction :)

in my main, I have: 

uint32_t value[2]; // start adc in DMA mode
int isSent = 1;
uint8_t tx_buffer[] = "Welcome to BinaryUpdates!\n\r"; 

int main(void)
{
 HAL_Init();
 SystemClock_Config();
 MX_GPIO_Init();
 MX_DMA_Init();
 MX_ADC1_Init();
 MX_TIM3_Init();
 MX_TIM4_Init();
 MX_TIM2_Init();
 MX_USART6_UART_Init();

 HAL_ADC_Start_DMA(&hadc1, value, 2);

 while (1)
 {
	 if (isSent == 1)
	 {
	 	 HAL_UART_Transmit_DMA(&huart6, tx_buffer, 27);
// HAL_UART_Transmit_DMA(&huart6, value[0], sizeof(value[0]));
	 	 isSent = 0;
	 }
	 HAL_Delay(1000);
 }
}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
	isSent = 1;
}