Unanswered Bed Temperature issues

Robo 3D R1 Plus (FIRMWARE_NAME:Marlin V1 / MACHINE_TYPE:ROBOR1PLUSV1)

Using OctoPrint for about a year now.

Prints have been fine until yesterday. Noticed that the bed temp that used to be solid at the set temperature is now varying about -4degC. Printer contiues to print without issue... Well until today. The set temperature does not move from ambient. The ambient of the bed matches the nozzle, so I that would indicate that the thermistor could be functioning (or at a low point that only reports what now looks like ambient )

Took the bottom off and;

• checked the power supply - GOOD
• turned on the bed temp (M140 S95.000); received OK but no power from the controller to the flat black cables - NOT GOOD

Thoughts? is it a RAMPS board issue? Can I find a RAMPS board for the R1+