I know this is a late reply, but when getting a project from iSpark to Spark, once exporting if from ISpark, if you change the extension from .ispk to .spk , it imports into Spark with no problems, now the issue Im having is importing from Spark into ISpark, you have to do the reverse, change the extension from .spk to .ispk. The only way to change the extension so that it work is select the Spark file get info ( comand i ) and change the extension there, but the issue Im having is that while it will import the sequence into ISpark, it doesnt import sounds from Spark, or rather Spark doesnt export the sounds. Im guessing since Arturia is trying to make money off the expansion packs, maybe they made it so you cant export sounds, but if you use your own samples in Spark Id hope youd be able to export them into ISpark, so far it seems you cant. If I have any luck ill post again.
Striz