Thanks for the quick reply. I eventually got it to work with the latest 4.2 Mono. I installed CleanMyMac and did a removal of PicoScope SW and then a full clean of machine. Then re-installed Mono, then Pico. Seems to work for now. i'll download the 4.0.4 version and keep your remarks in mind if Pico...

Just bought a Macbook 12. Pico 6.11.8.11 will not open at all.
Installed Mono 4.2.102 tacos.xamarin.x86 (a link to the PROPER installer of Mono, might be beneficial in the Pico Installer at bottom).

Can anyone suggest where I should go from here?