This seems a common issue, and I have followed solutions provided in past answers, to no avail. What I have found that if I turn off the BMPRO Genius-II series power supply that supplies all 12v in the van and charges the battery, the Victron BMV-712 starts to display current values. I can understand that the power supply could be supplying power and therefore there is no discharge from the battery therefore may show 0.
The BMV-712 replaces a BMPRO BATTERYCHECK Bluetooth shunt, that always showed voltage and amperage on charge or discharge.
When initially connecting the BMV-712 The battery had not been on the trickle charge as supplied by the Genius-II for a number of days. When I initially connected the BMV -12 after installation it, showed a voltage that slowly increased as expected due to the charging cycle, but the amperage remained at 0. It is only when the power is turned off on the Genius-II do I see any values - values as the battery is in discharge. When I turn on the Genius-II again I do see the amperage show + values as the Genius-II is back in charge mode, but after a short period the amperage reverts to 0.
I have included a copy of the wiring diagram below.
Any help is appreciated, thank you