I sorted this - problem was indeed driver related - but not st-link - it was libusb - in case anyone else runs into this problem.
I should just point out that platformio is too slow to use. It takes 30-40 seconds to fire up the debugger, builds are slow, it hangs my VI extension all the time, the intellisense is barely functional. It’s a pity because it shows real promise as an IDE - i’ll come back and look in 6 months maybe.