To Troas (eis tēn Trōiada). Luke does not mention this stop at Troas on the way from Ephesus to Macedonia (Act 20:1.), though he does mention two other visits there (Act 16:8; Act 20:6).
When a door was opened unto me (thuras moi aneōigmenēs). Genitive absolute with second perfect passive participle of anoignumi. Paul used this very metaphor in 1Co 16:9. He will use it again in Col 4:3. Here was an open door that he could not enter.