When you try next week, try this:
-Feed after dark and at night- ball pythons are nocturnal.
-Pre-scent the room for an hour at least. Put the mouse in a small container with holes in it right next to the tub and really let the snake know that prey is near.
-Put the prey into the tub using as little light as possible to do this.
-Tippy toe out of the room and don't let anyone into the room and keep the room dark.
-After 30 minutes, tippy toe into the dark room and very quietly check if the mouse has been eaten. If not, leave alone for another 15 or so minutes.
-If the mouse is still there, keep it alive for another week and try again.

Some things to check:
-Is the tub too big for the snake?
-Is the temp at about 94F? Warmer temps will increase appetite.
-Does the snake have a very tight fitting hide?

Let me know how this works. I have a snake who was a miserable eater and was beginning to really lose weight. This methodology was taught to me by Becky (satanicintention) and has worked extremely well. My little hypo has more than doubled in weight and is right now eating her second mouse of the night!!

Take care and good luck!