Hi, I use an Arduino with the Me Uno shield and have found that at least the board does not work in the scratch mode with mBlock 3.3.3 and 3.3.4.
Me Orion works with 3.3.3 (3.3.4 not tested)
I can connect with the Board and upload the firmware well - but when I click the green flag, nothing happens.
With mBlock 3.3.0 everything works as expected.