The reason that the uro won't come out if it's too cool, is that it's body thinks it's still supposed to be brumating until the temperature heats up enough to come out.
Your uro should definitely have a hotter basking spot. Try to get it up to about 125-130F, with an area wide enough for your entire uro to be under the warm area. Try using a hotter bulb, and make sure it's either a flood, or "NOT" one of the narrow-beam reptile bulbs so that you have a wide enough hot area.
Nicki
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Nicki and...
0.0.2 Uromastyx geyri (Saharan Uromastyx) - New babies! 
1.1.0 Uromastyx dispar maliensis (Mali Uromastyx) - Spike and Lizzy
1.0.0 Lampropeltis mexicana thayeri (Variable (Thayer’s) Kingsnake) - Kavi
0.0.1 Lampropeltis triangulum campbelli (Pueblan Milksnake) - Callia
0.2.0 Thamnophis sirtalis parietalis (Red-Sided Garter Snakes) - Spot and Fluffy
Ontario, Canada