My bad, yes this needs to Python3 style print statements with (). Copied it from SigFox MKR1200 Unit Testing - If you don't see any output for the first 10 secs, please reset board - #4 by isa56k.
This is still a mystery to me. When doing pio run -t upload in the PlatformIO CLI, does the serial monitor open too or does that behave correctly? Otherwise I’d recommend a re-install of the PlatformIO VSCode extension if that is bothersome o_O