I have an STM32F411 on a PCB and I tried to connect it to the ST link using STM32 ST-Link Utility app but I get the error Cannot connect to target! Please select 'Connect Under Reset' mode from Target->Settings menu. If you are trying to connect to a discovery board, please select SWD mode from Target->Settings menu.' But there is no 'Connect Under Reset' mode in that menu (and the SWD mode is greyed out). In firmware version, it just says USB communication error. I have tried connecting with reset on, cycling reset, pressing the full chip erase button while reset is on then turning reset off. Nothing changes except now the error is just USB communication error.
I then tried connecting it instead to a Nucleo-F411RE board and the same thing happened.
Any help would be great