The 15x1 is the "regular" needle, so if the repair guy said it was too long, it's possible it takes the very short Wilcox & Gibbs Needle. (it's not the same as the Singer 24x1) the 15x1 is a quite short needle compared to many vintage sizes.
It's possible the machine was made both in full size and toy, and that is why it's shown as taking the 15x1 needle, but it does not fit the toy machine.