What exact command are you using?
make run_debug PROGRAM=demo_gpio
Works for me on the hifive1 but I have to kill openocd by pid later.
You can also supposedly run openocd in one terminal and gdb in another terminal, but I haven’t tried that. mwachs5 posted some instructions for that a few days ago. Problems w/ run_debug, run_openocd, run_gdb make targets w/ E300 Arty