We see not our signs. Some suppose "standards" to be meant, as in Psalms 74:4, where the same word is used; but it is, perhaps, better to understand, with Dr. Kay, "Divine ordinances, which were standing signs of God's presence—as the tabernacle, the sacrifices, the sabbaths."
There is no more any prophet. It has been said that this shows the psalm not to have been written on the occasion of the destruction of Jerusalem by Nebuchadnezzar, since Jeremiah, Ezekiel, and Daniel were, all of them, then living.
But the writer only means to say that there are no prophets in Palestine, where he is residing. Jeremiah in Egypt, Ezekiel on the banks of Chebar, Daniel in Babylon, are nothing to him, even if he knows of their existence, and in no way fill up the gap whereof he complains.
Neither is there among us any who knoweth how long. Jeremiah's prophecy of the seventy years (Jeremiah 25:11, Jeremiah 25:12) did net remove the doubt, since it was uncertain from what event the seventy years were to be counted.
Jeremiah's prophecies, moreover, were not yet, in all probability, collected into a volume, and so may not have been known to the psalmist.