This is probably due to Jupiter being an extended object (disc) and the Bahtinov Mask is really designed for focusing on pin point objects (stars). IIRC, a disc can be seen to be made up of a necklace of “points” and this apparent multitude of points may be confusing the optimal focus?
I have successfully focused on the Galilean moons of Jupiter, but only used Jupiter’s disc to obtain coarse focus.
Cheers
Dennis