can you see any files on the card?

can you browse to other directories on the SD card? there are presliced gcode files on factory sd card.

Thermal Runaway, system stopped! Heater_ID: bed - Printer halted. kill() called!

after this issue occurred, i rest the printer and set to pre heat bet to 60C after 20 minutes there was a time where the bed temp gradually dropped off to 56C for less than 1 minute then returned to 60C for 50 minutes then temp dropped again to 54 and had error "occurred"

my logic: if it were a thermister issue it would not show a gradual decrease and then a gradual increase to back set point and i would expect to see more erratic temperature readings.

i am trying to get a digital thermometer to monitor bed temp, or should i just replace the bed?