Anyway - I find if you pop a nice new house in that's good for nesting they will move in and be happy
If it's big enough. If it's too small or not dark inside it may be ignored. Put a smelly treat inside like a piece of cucumber to tempt the hammy in and they tend to move in overnigth and build a nest. Torn up strips of plain white toilet paper are the safest nesting material and they like it. Put a heap of it in the cage (but not in the house). They forage for it, take or pouch some and take it to build a nest.
Tip - I leave the nest alone unless it's pee'd in - they are very fussy about their nest and tend to refurbish it themselves.