What is the Shut Door of this Parable?

What is to be understood by the open and shut door in the scripture just quoted? We think a satisfactory answer to the question may be found in the accompanying explanation: While there were those among the Adventists who had received advanced light, and were teaching that the Saviour had changed his service from the first to the second apartment of the heavenly sanctuary, and were correctly presenting the open and shut door question to those who would hear, another class opposed this truth, and were trying to establish faith in the doctrine that the open door was closed, and the closed door open. In doing this they were hedging up the way, or hindering the work, of the Lord’s servants here on earth. The doors of the heavenly sanctuary are opened and closed by the power of Christ—“He that openeth, and no man shutteth.” In the address to the Philadelphia church, the people who hold fast, keep the word, and do not deny his name, gain a victory that opens a door that no man can shut. This undoubtedly refers to the door of access to the people, which door men, seemingly (as we shall see), had effectively shut; but as a recognition of their steadfastness, the Lord sets before the faithful an “open door” that no man can shut.GSAM 217.3