Why does it say "Ososeinu Lo Ra'inu"?
Rashi: The signs that our Nevi'im promised us. We do not see them in the long exile. Asaf had this Nevu'ah about Galus.
Radak: We do not see signs of the redemption, even though the Galus has been long.
Why does it say "Ein Od Navi"?
Radak #1: There are no more Nevi'im from the time of Galus. After Chagai, Zecharyah and Malachi died, there was no other Navi to tell the future, and when the redemption will be.
Radak #2: The Navi did not come yet. I.e. the Navi who will appear to us close to the redemption, Eliyahu ha'Navi, did not come yet.
Malbim: Hashem's dwelling in the land used to be revealed via Nevu'ah - now there is no Navi!
Why does it say "Ad Mah"?
Rashi: Until when [will we be in this affliction]? Radak - this is like "Ad Mah Hashem Te'enaf la'Netzach" (79:5).
Malbim: Hashem's dwelling in the land used to be revealed via Ru'ach ha'Kodesh - now we do not know "Ad Mah"?
