I started using this binding some two weeks ago.
As far as I understand, you need the paid account. The free one did not work for me either.
But for me so far I chose only ChatGPT 3.5turbo, which is billed by token count. One usual query plus answer in average costs less than a tenth of a cent.
Another good thing is, they support prepaid billing. Full control. So I charged it with 5 Euros which will probably last for months 
From there on the binding worked reliably.
One drawback I found was that it seems that the binding does not support chat context. So everything you do is only valid for one command, no actual conversation or pre-prompting possible. Yet I am not sure if this is really the case or if I missed something, I opened a topic right today… See here.