Had a similar situation with my MultiPlus-II 48/8000 last winter — absolute nightmare. One day it just went dead, no LEDs, no signs of life. Batteries were fine at 50V, no burnt smell or visible damage.
Turned out to be a firmware corruption issue after a power surge from the generator. Victron support walked me through the recovery process — you need the VE.Can interface and a laptop to reflash it. Took about 30 mins once I had the right cable.
Few things worth checking first:
DC side — Make sure your battery connections are genuinely solid. Loose terminals can cause strange lockups. I'd disconnect and reconnect everything, check for corrosion.
Mains input — If it's permanently off-grid like mine, this shouldn't matter. But if you've got grid backup, try removing the AC input entirely and see if it responds at all.
Control side — Are you running it standalone or with a GX device/Colour Control? Sometimes the comms module gets stuck. Try a full power-down (disconnect batteries for 10 minutes) and cold restart.
The fact there's no burnt smell is actually encouraging — suggests it's not a catastrophic component failure. More likely firmware or control board glitch.
What's your setup? Standalone or integrated? And does it respond at all when you try to force a soft reset through the control inputs? Might help narrow this down before you contact Victron support.