It says "as many who were appointed to eternal life believed". That explicitly shows not everyone is appointed to eternal life, and that would exclude the unbelieving Jews, hence their lack of belief.
48 And when the Gentiles heard this, they were glad, and glorified the word of the Lord: and as many as were ordained to eternal life believed.
Please note that the word "ordain never fixes anything absolutely. (Lk. 7:8; Rom. 13:1; Acts 28:23, Matt. 28:16; 1 Cor. 9:14; 7:17) Paul ordained some things and that no more meant they were absolutely fixed to come to pass than if he hadn't used the word(Rom. 13:1).
The meaning is obviously that as many as were disposed to believe the message, believed.
(Rom. 2:7) - God doesn't ordain any Gentile to eternal life until he has followed his conscience and is willing to hear the Word of God (vs. 42,48) "ordained" something God allows to come to pass. God allowed the Gentiles to hear the gospel message. The order was, Jew first, then Gentile. That's the order God ordained.