USB serial don't work for STM32F7

Hello, i tried ot start the USB serial connection on a STM32F7 to get some debug messages, but it doesn’t work. When the program is started, it stops on this function: sem.try_acquire_for(rel_time).
Does anyone have the same problem or can help?


I not tested it so deep but the example USBSerial seems be ok - 2x usb cable (St-link and USB-OTG), Nucleo-F767ZI, MbedOS 6.5, MbedStudio and serial terminal with DTR signal ON.

BR, Jan