Hi romi,
It could be that you need a version of Max/Msp on your computer:
Specifically, the Windows-version of MEA sometimes needs an installation of Max/Msp from Cycling74, because some necessary components may be missing on your PC.
In other words:
a) please let me know which OS you are on
b) try installing Max/Msp from cycling74.com
–> you do not need to buy a license in order to run MEA
Cheers, Fabian