We have a custom designed STM32L151R board. We have not been able to flash the code using the flash loader application (demonstrator gui) . We are able to load the code using ST-Link and the serial port works properly when configured through the code. Is this an inherent problem of the controller or are we doing something wrong? We need to get the serial boot loader working as there may be site updates. Thank you for your time. Awaiting your suggestions to solve the problem.