How do 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 - "Ki Shachan alav he'Anan", confining Moshe's inability to enter the Mishkan to when the Cloud rested on it and the Shechinah filled it, 2 and establishing the Pasuk in Naso when it had departed. 3
To what extent was Moshe unable to enter the Ohel Mo'ed?
Ramban #2 (on Pasuk 34): On account of the Cloud that enveloped the Mishkan and the Shechinah that filled it, He was forbidden to enter the Ohel Mo'ed without permission. He was permitted to enter however, when Hashem called him. 1
Ramban #3 (Ibid.): 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 (Ibid.): According to the Toras Kohanim, 3 once the Cloud was no longer resting on the Mishkan, 4 Moshe was permitted to enter, either uninvited, or, when he heard Hashem calling him from the lid of the Aron, he entered and stood in the Heichal in front of the lid of the Aron.
As was the case at Har Sinai (See Shemos 24:16 & 18), and as is implied in the opening Pasuk in Vayikra (Ramban).
As the opening Pasuk in Vayikra may also mean (Ramban).
And the opening Pasuk in Vayikra refers to the seven days of Milu'im, before the Cloud filled the Mishkan (See Rav Chavel's footnotes).
And 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