I would suggest trying all the aboves suggestions first. That's all sound and detailed advice.
I am no expert. (new to ball pythons but not snakes) but I would suggest, If after some time, that does not work, try a different pray item, ASF/multies or mice, and maybe consider smaller.
How big is your snake?. If its a live feeder I avoid hatchlings, because you have a lot more time with older snakes before a fast harms them. Harming them is the last thing we want.
Also its worth checking with the breeder about what housing its used to and what substrate, matching it can help settle it in faster.
To respond to the time question. For me at least it varies, Sometimes its really fast, others it takes ages.
Just an opinion based on my limited experience with ball pythons.