Help my baby indian ringneck wont eat!?

  hmmm, we a currently handfeeeding her, but due to the out of date of her formula, we had to switch to another one, as soon as we gave her the new formula she only seems to be interested in the first bit of feeding, ( the first bit of formula we feed her) and then when we try to feed her some more, she stays quiet and doesn't open her mouth, please help!, we have to force feed her now and it makes me feel so bad, will she get used to this formula, shes currently been on it for 2 weeks.

She is a very lively bird and healthy, but i just wanted to know whats wrong with her:/

she is about 5 weeks old!

And when we she be ready to start eating seeds?
Birds can start eating seeds once their beaks get smaller when they aren't as big as their head and when their fluff starts turning into feathers but idk about the other stuff