Where is the temp gauge located? On the wall of the tank?

Rosies mostly use conduction to heat up. They butt up against a warm surface. The air temp can be 60 deg, but if the object (like a sun-warmed rock) is 85 deg, then the rosy can warm up.

What you need to do is have a large heat pad - big enough for the rosy to coil up on if she wants, or even bigger, since your cage has plenty of room for unheated area - and use a temp controller to keep that heat pad warm enough to get about 85-90 at the surface.

Don't use very much substrate if using wood chips. That ends up insulating the heat to stay below the substrate. What substrate are you using?
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Mark