Since it worked after power was removed and then restored, it appears to be that the microcontroller had to be reset (and removing power did that). If it happens again I recommend you place a 12V boost/buck converter in the MaxFax's feed circuit. Reason is that some MaxFans will malfunction with this condition if their input voltage rises above 15 or so volts. Since some
solar controllers (mine included) will temporarily output this higher voltage as part of their charging profile, the buck/boost converter is needed to keep the MaxFan "happy."