Small Royals not eating is linking to husbandry almost exclusively. It is usually heating or security. Humidity usually has no impact directly on feeding, it is linked to illness. Illness is another reason why a snake of this size will not feed.

A rack will complicate the issues for heating and only exchanges the one set of problems for another set. The range of solutions with a rack are limited comparatively speaking.

What is your current enclosure?

Do you have 2 hides and are they correctly sized?

Do you have 'cover' over head?

What are the temps under the hot side hide?

Under the cool side hide?

The ambient air temp in the enclosure?