But - transitional conjunction. But “now” to pass to another subject.
in the Lord - He views everything with reference to Christ.
at the last - “at last”; implying he was expecting their gift, not from a selfish view, but as a “fruit” of their faith, and to “abound” to their account (Phi 4:11, Phi 4:17). Though long in coming, owing to Epaphroditus’ sickness and other delays, he does not imply their gift was too late.
your care ... hath flourished again - Greek, “Ye have flourished again (revived, as trees sprouting forth again in spring) in your care for me.”
wherein ye were also careful - in respect to which (revival, namely, the sending of a supply to me) “ye were also (all along) careful, but ye lacked opportunity”; whether from want of means or want of a messenger. Your “lack of service” (Phi 2:30), was owing to your having “lacked opportunity.”