I have the same problem. I started Mbed studio and tried running the mbed-os-example-blinky. I used the NUCLEO-F401Re board, which is recognised by MBED studio. However, I cannot expand the mbed-os-example-blinky in the workspace. A rotation sign appears.
Error: kill ESRCH
…with sub-errors pops out.
I tried reinstalling MBED Studio, but the problem remains.