I'm not sure it's a con, but the lack of public demonstrations suggests that whatever they think they've got isn't what they've actually got, so attempts at replication don't work consistently.
attempts at replication don’t work consistently.
***Replication only needs to happen once. The effect has been replicated thousands of times. Consistency is a completely different matter, requiring engineering diligence and resources. If 5% of the resources dedicated to hot fusion had been poured into LENR, you would have your LENR hot water heater by now.