You're going to want to check SE502 , that dictates MA202 to charge the brake accumulators. If all the oil is being thrown at the brake accumulators, there's none left for the fan.
For testing, curl your bucket back over relief, hold it for 10 seconds. That should satisfy brake charging. If the fan has not engaged, that's an indication that the sensor or fuse may have failed. I believe it is f22 that feeds the sensor. Check the sensor itself to verify power on one side of the connector. Please report findings.