Thank Achiel! that's it.
zipped the project folder, and converted it, almost happyness....
>mxconvert "E:\Mendix Project\TestMx6.4.1\TestMx6.4.1.mpk" "E:\Mendix Project\TestMx6.4.1\TestMx6.6.0.mpk"
This is MxConvert, version 6.6.0.
Unpacking the input mpk file 'E:\Mendix Project\TestMx6.4.1\TestMx6.4.1.mpk'.
Found the input mpr file 'C:\Users\andri\AppData\Local\Temp\tfassnp0.kf0\TestMx6.4.1.mpr'.
Checking the version of the mpr file.
The mpr file version is '6.4.1'.
Converting the mpr file.
Checking project for errors.
The project contains 14 errors, 20 warnings and 0 deprecations.
Saving the converted mpr file.
Exporting the output mpk file 'E:\Mendix Project\TestMx6.4.1\TestMx6.6.0.mpk'.
Removing temporary files.
MxConvert finished.
Next thing... the command line shows that there are errors......and warnings... Though the app is running fine in 6.4.1 and opening the converted (onzipped) file in 6.6 does not show any error too.
In the output we see, of course, that the deployment and packages folder are not copied.
What are these error? And where are de log files or the output?