After spending a day to get the OpenSDA debugging going I found a blog saying that I had to replace the boot app with DEBUG-APP_Pemicro_v108.SDA . So I did, now my host PC cannot see the device anymore when I power it the normal way. It has also disappeared from the device manager. I tried a few other boot apps but the result is all the same - the device looks dead when powered on. No LEDs blinking, no PC enumeration. The only thing that works is getting back into boot loader mode.
I would appreciate any help, thanks in advance!