The question of the Holy Spirit not being present during the tribulation results from a misunderstanding of 2 Thessalonians 2:7, “For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.”
Right now, prior to the tribulation, one of the ministries of the Holy Spirit is the restraint of evil. In 2 Thessalonians 2:8-9, we learn that the restraining power of the Holy Spirit holds back the “lawless one” (Antichrist) so he is not revealed before God wills it. The passage says the Holy Spirit will no longer restrain the growth of evil, but that does not mean He will have no ministry whatsoever.
In Acts 1:4–5, Jesus promises that His disciples would soon be “baptized with the Holy Spirit.” In Acts chapter 2, Jesus’ promise is fulfilled. “Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.” Acts 2:38–39
The indwelling of the Holy Spirit is assured for every born-again believer, and nowhere in Scripture is that promise rescinded. Regeneration is the Spirit’s work; without Him, no one is saved. If the Spirit were not present during the tribulation, no one could be saved. But the fact is that a multitude that no one can number is saved during the tribulation (Revelation 7:9–14). Therefore, those who come to Jesus during the tribulation period will also be indwelt by the Holy Spirit. This who will be saved during the tribulation, will need the guidance and direction of the Holy Spirit during that troubled time.
Another good reason that the Spirit must be present during the tribulation is that He is omnipresent. Since He is everywhere at all times, He must be in the world during the tribulation.
At some point—only God knows when—the restraining influence of the Holy Spirit will be removed, the Antichrist will be revealed to an unwitting and unsuspecting world, and the tribulation period will begin.