@diyguy if your core responds to commands in MIOS studio, it might not be toast - if you’re building a LoopA, check that you’ve installed R101/R102 - if not, the core may be stuck in bootloader mode, as Andy said.
If these are installed, as Andy also suggested, i’d recommend to get an original ST-LINK V2 and reflash directly via JTAG - you could follow this nice tutorial by @Phatline :
Best regards,
Peter
