There's types of proof for a case like is proposed that are difficult enough to fake and easy enough to test that the failure to even make the attempt is damning.
For an energy source that is supposed to be able to provide steady-state energy supplies, a steady-state power analysis is a test that is so blindingly obvious to perform that the lack of one is a major alarm bell.
To do a steady-state test you take a system like the one they are showing off, go through the tests that they have displayed, then when the output temperature stabilizes you put a load on the output. The load in this case could be a simple steam engine instrumented to read the output power, though any sensor suite that could measure flow+temperature+pressure would suffice.
The key to the steady-state power analysis is it starts at the end of the tests they have released.
There are other tests that would show what is going on internally that would prove or disprove their claims for a mechanism quite clearly, but they have consistently denied the level of access required for an independent researcher to perform an isotopic ratio measurement or any similar test.
It is the lack of tests that demonstrate what they are claiming to produce as well as failing to give evidence for their proposed mechanism that cause me to dismiss their claims out of hand.