hypeDiscussions 3.1.1 causes Server 503 Error


I'm running Elgg 3.3.11 and have attempted to run hypeDiscussions 3.1.1 within a closed group.

The dependency HypeInteractions 6.2.1 is installed, and I have site wide duscussions switched off (groups only)

When I  go into the group as site admin there are no problems and  the features are superb, however when anybody else (Group Members - it is a closed Group) goes into the group they get a 503

Is anyone else using this plugin and experiencing the same?

Any help would be greatly appreciated, the plugin appears to do everything I want, I just need to get it running :-)