When did this Pasuk take place?
Ramban (earlier on Pasuk 5): It took place on the eighth day, when the Shechinah came to rest in the Mishkan.
Rashbam (on Pasuk 35): To demonstrate Hashem's love of Yisrael, no sooner had Moshe finished setting up the Mishkan than the Shechinah rested in it,
and Moshe was unable to enter.
Seforno: As soon as Moshe had finished setting up the Mishkan and performing the Avodah in it.
Both the Rashbam and the Seforno (Refer to 40:34:1:3) are referring to the eighth day, like the Rashi cited by the Ramban (Refer to 40:34:1:1*).
This was only temporary, however, since the Shechinah subsequently moved to atop the Aron ha'Kodesh, from where It spoke with Moshe (See 25:22). Refer also to Vayikra, 1:1:10.
Why does it say that Hashem's honor filled the Mishkan?
Hadar Zekenim: Really, Hashem constricted His honor, and the Mishkan filled it. It is more honorable to say that His honor filled the Mishkan, for this implies that it is bigger than the Mishkan.