I really don’t have a good feeling about the health of your mainboard but #3 should be diagnosed before you give up all hope.
Inspect all the wiring for loose connectors and damaged wires. Be sure to remove the cover off the extruder and check the connectors on the circuit board where the ribbon cable attaches.
On my SV07 the ribbon cable got between the frame and the extruder. After homing 30 or 40 times the extruder slamming into the cable cut the first wire on one edge. On the SV07 that is a thermistor wire.
If the printer still won’t boot then open Fluid and rename printer.cfg → old_printer.cfg. Upload the one below, save and restart. This configuration has no reference to any thermistors and won’t print. It may, however, boot and flag errors that don’t trigger emergency shutdown.
I will give this a shot. The main board is brand new. I ordered it about 3 weeks ago, took 2 weeks to come in. Hopefully not the main board, but oh well if it is. I’ll let you know what I find with your instructions
OK, so, happy update. @cardoc your advice about checking wires paid off. I had 2 seperate wires that were no longer in there connector. That’s some micro work. Once they were put back in, everything came up and started working. I’ve got the first test print going now.