Congratulations on the new TT -hope you get the problems sorted out soon- and welcome to the forum.
My trailer isn't here so I can't verify this, but as I recall there is a position for the fan on the thermostat labled 'On' and 'Auto'. Your trailer may be similar. Check the fan switch on the thermostat.
Sherm & Terry w/rescue Eydie (min Schnauzer) & Charley (std Poodle)
2015 Jay Flight 27RLS (Nights Camped: 102 '15, 90 '16, 80 '17, 161 '18)
2006 Ford F350 6.0 PSD, 4WD, CC, LB, SRW, Camper pkg, Equal-i-zer, GY Endurance (E)