Do you have any messages?
In first time check the coolant pump with hand and you can check the info about the pump rotations in user interface? Click on the top right square with info about main tanks. Take a picture or see what happens with pump.
Do you feel the temperature on heater or on coolant manifold?
Check what happens in coolant container? Do you have coolant flow? Do you have coolant in system?
If you have a coolant in the system, if the pump is rotating and you can see some bubble moving in the hoses, if there is a coolant movement in the coolant container, if you feel temperature after touching the manifold or heater with your hand, then the coolant system is working.
When and how did this happen? Inspect all cables between the PH's boards and the heads, between the PH's boards and the carriage board.
You can generate a log and send it to me by e-mail. You may have a problem with fireware cable and so on ...
Now you will need a service key to check what happens with print head termistors.