I don't know the specifics on where issue with the Hypervolt integration arise. IO Go requires two-way comms to the charger/car. One direction to set the charge the other to confirm that it has happened. This can breakdown. Though charger integration generally more reliable than vehicle.
AC EVSEs tell the onboard charger how much current is available by putting out a pulse over the Control Pilot pin. Depending on the duty cycle that will indicated that anywhere between 6A and something like 60A per phase are available. A lot of EVSEs set the PWM duty cycle to 0% when the vehicle is plugged in but it is outside the the scheduled charge time. While this is not strictly necessary, as I think 6A is at something like 46% duty cycle, there are reasons not to always put out a live PWM. It seems that the OBC control software on some cars uses the presence, or lack thereof of a PWM singnal to decide whether or not to sleep. This seems to be the issue with at least some Renault implementations, where it seems to affect newer cars. If there is no PWM for a given amount of time the car goes to sleep and will not recognised when the PWM duty cycle goes above 0, unless some other intervention occurs, eg unlocking/locking the car. This is all over many Renault forums, for the Megan and now Scenic. I don't know how universal it is by model and how many chargers fall afoul; however, I have seen Ohme and Zappi called out along with some public AC sites.