Restart a dead battery?

I left my van for two weeks; thought I had turned off all loads. Came back and all displays are flat - Kisae DMT1250 doesn’t respond with engine running, Victron 702 screen is blank. No charge accepted with engine on. Hooked a battery charger directly to cable leads to the battery with no result. How do I restart the BMS? Apparently everything drained and hopefully the BMS low voltage protection kicked in. Where to go from here?

Greg