Israel's New Covenant (Jeremiah 31:31) did come in at or about Pentecost (as evidenced by the gifts of the Spirit) but phased out in Acts 28:28, when Israel temporarily became "not God's people" and the salvation of God was taken from them and sent to the Gentiles. Since the nation of Israel does not exist today, in God's eyes, the other things belonging exclusively to Israel (New Covenant and the Gifts of the Spirit, etc) also have temporarily ceased to exist in this parenthetical 2000 years long age that we live in. All of Israel will be back on the scene for the tribulation.
Acts 13, has the gentiles preached to and also believing. So do not make a doctrine on Acts 28 being a turning point of destiny for Israel.
Israel also was not believing in Christ and it says they could not believe in Him to fulfill the scriptures as God had so spoken of them in John 12 during the days of Christ on the earth. What happens is similar to the Isaiah 6:9-10 scriptures in John 12, however the few elect among them did believe, as also the elect among the gentiles did believe.
God did not just give up on converting any jews at Acts 28. This was predetermined that the gospel went out to the entire earth, to the gentiles, yet still only the elect of both Jew and Gentile ever did or will believe and be saved.
Acts 13
48 Now when the Gentiles heard this, they were glad and glorified the word of the Lord. And as many as had been appointed to eternal life believed.
44 On the next Sabbath almost the whole city came together to hear the word of God. 45 But when the Jews saw the multitudes, they were filled with envy; and contradicting and blaspheming, they opposed the things spoken by Paul. 46 Then Paul and Barnabas grew bold and said, “It was necessary that the word of God should be spoken to you first; but since you reject it, and judge yourselves unworthy of everlasting life, behold, we turn to the Gentiles. 47 For so the Lord has commanded us:
‘I have set you as a light to the Gentiles,
That you should be for salvation to the ends of the earth.’”
48 Now when the Gentiles heard this, they were glad and glorified the word of the Lord. And as many as had been appointed to eternal life believed.
49 And the word of the Lord was being spread throughout all the region.50 But the Jews stirred up the devout and prominent women and the chief men of the city, raised up persecution against Paul and Barnabas, and expelled them from their region. 51 But they shook off the dust from their feet against them, and came to Iconium. 52 And the disciples were filled with joy and with the Holy Spirit.
Romans 11
7 What then? Israel has not obtained what it seeks; but the elect have obtained it, and the rest were blinded. 8 Just as it is written:
“God has given them a spirit of stupor,
Eyes that they should not see
And ears that they should not hear,
To this very day.”
John 12
Who Has Believed Our Report?
37 But although He had done so many signs before them, they did not believe in Him, 38 that the word of Isaiah the prophet might be fulfilled, which he spoke:
“Lord, who has believed our report?
And to whom has the arm of the Lord been revealed?”
39 Therefore they could not believe, because Isaiah said again:
40 “He has blinded their eyes and hardened their hearts,
Lest they should see with
their eyes,
Lest they should understand with
their hearts and turn,
So that I should heal them.”
41 These things Isaiah said when he saw His glory and spoke of Him.
God blinded Israel deliberately according to His purpose and will so that it says, they could not believe in Christ.
Coming to God through Christ is by divine appointment alone, that is His will, so that no flesh can glory in His presence but only depend on His mercy and compassion. Many christians I think do not believe this, but rather believe in mankind's free will destiny. But obviously here for Israel, there was no freedom of the will to believe in Christ as God had blinded their eyes and hardened their hearts against believeing in Jesus Christ, and so they were most of them not saved.
Romans 11
7 What then? Israel has not obtained what it seeks; but the elect have obtained it, and the rest were blinded.
That would be the elect Jews and the elect Gentiles did obtain salvation with the rest of all people everywhere being judiciously blinded and having their hearts hardened by God according to His purpose and will.