Note 12 at Gal. 4:19: Through prayer, Paul had interceded for these Galatians when he first brought the gospel to them. Now he is in doubt of their relationship to Christ since they are moving back toward trusting in the law. Therefore, he is praying for them again as he did in the beginning.

This does not mean that these Galatians have lost their salvation and Paul is praying for them to be born again again. That can't happen (see note 5 at Acts 5:5, p. 595). He is simply stating that he wants to see the Galatians turn back to Christ and develop and grow in Him again.