Hi,
PIN 7 communicates a signal that the inverter is allowed to turn on or not. There are low level reasons that this has a dedicated pin, like for low powered BMS safety states where the inverter should be really off as much as possible to prevent a phantom discharge load from further draining an already flat battery that has no other method to protect itself.
In this case, for some reason that method is not behaving itself, and either the GX device is not sending, or the inverter is not receiving the conditions it wants to allow it to turn on.
All other communications are handled completely differently on other pins. This cable with a removed pin 7 will the be the (semi)permanent connection, unless we are able to further resolve why this might be occurring.
But in all cases till now, it resolves the situation without any real drawbacks.