A.T. Robertson Commentary 2 Corinthians 2:12

"Now when I came to Troas for the gospel of Christ, and when a door was opened unto me in the Lord," — 2 Corinthians 2:12 (ASV)

To Troas (εις την Τρωιαδα). Luke does not mention this stop at Troas on the way from Ephesus to Macedonia (Acts 20:1f.), though he does mention two other visits there (Acts 16:8; Acts 20:6).

When a door was opened unto me (θυρας μο ανεωιγμενης). Genitive absolute with second perfect passive participle of ανοιγνυμ. Paul used this very metaphor in 1 Corinthians 16:9. He will use it again in Col 4:3. Here was an open door that he could not enter.