How can we reconcile the Pasuk here, which states that Moshe was not able to enter the Mishkan, with the Pasuk at the end of Naso "u've'Vo Moshe el Ohel Mo'ed Ledaber ito ... "?
Rashi and Ramban (citing the Toras Kohanim): Comes the third Pasuk, 1 and issues a compromise
Rashi writes that Moshe could not enter the Mishkan when the Cloud rested on it and the Shechinah filled it. How could Hashem talk with Moshe all this time, and how could they burn the Ketores, light the Menorah and arrange the bread?
Ramban #1 (on Pasuk 34): He could not enter without permission, but he could enter when Hashem called him. 1
Ramban #2 (34): Moshe did not enter the Mishkan at all. When Hashem called to him from the Ohel Mo'ed, he stood at the entrance and Hashem spoke to him from inside. 2
Ramban #3, Moshav Zekenim #1: The Cloud rested on it only on the eighth day, and Hashem spoke with him beforehand. 3
Moshav Zekenim #2: After the Cloud rested, it alighted to on top of the Aron.
As was the case at Har Sinai (See 24:16, 18), and as is implied in the opening Pasuk in Vayikra (Ramban).
As the opening Pasuk in Vayikra may also mean (Ramban).
Ramban: The opening Pasuk in Vayikra refers to the seven days of Milu'im, before the Cloud filled the Mishkan (See Rav Chavel's footnotes). Moshav Zekenim - the initials of "Shachan Alav he'Anan" spell "Sha'ah", to hint that the cloud was on for only a short time.
To what extent did the Shechinah dwell in the Mishkan?
Seforno: On the one hand, it filled the Mishkan, and did not extend one inch outside it; 1 on the other, it remained constantly in the Mishkan, and did not move from it until the time came to travel. 2