After playing with the 3.0 beta it seems that certain apps will not function. Some are used often (the problem I found was with the Mxmodelreflection). Must all apps be upgraded to a 3.0 version? I assume the Mendix apps will get an upgrade soon?
We are migrating the apps one by one. If you cant wait for that; just import the module in Mendix 2.5.5 en convert the project to Mendix 3.0 and export the module again. That should work for most modules.
After reading your other post, but this wont work for MxModelRefelection, since it is not compatible with 3.0 yet.