@soren_kurgan_jacobse the part on the right is the thermocouple. Before I tell you to disassemble anything (and I won’t) I found this on the Makerbot support site:
“This means that the bot is looking for temperature readings and not finding them. If you’re using a single-extruder Replicator or a Replicator 2, go into the Utilities menu on your bot, choose “General Settings,” and check that Tool Count is set to “Single.” If it’s set to “Dual,” the bot will think it’s supposed to be getting readings from two extruders. If that’s not the problem, check both ends of the heated build platform cable and the thermocouple connections on the motherboard. You can clear this message by hitting the M button.”
Have you checked this setting?