Hi...
The first thing to check is that AccuRig is functioning correctly. So go to "File > Load Sample Character" and go through the rigging process with a sample character and see if this works fine.
If it does work with the sample characters, then the issue is likely with the Blender model itself. Please let us know the polycount of the model as this can be an issue. Do also make sure you have plenty of free hard drive space available as sometimes low space can lead to loading errors.
Peter
Forum Administrator
www.reallusion.com