Anyone who is interested in the subject ought to read Graham Hancock's book, Sign and the Seal. Hancock's timeline is much more persuasive than the Kebra Negast and there is secular evidence to support it.
Hancock says the Ark was removed from the Temple by the priests during the reign of Manasseh, Hezzikiah's son, in the 7th Century BC and taken to Elephantine Island in Egypt.
Manasseh denied God and profaned the Temple.
And there is secular evidence that there was a Temple on Elephantine built at this time. There is existing correspondence between priests at that Temple and the priests in Babylon during the captivity.
Problems developed in Egypt in the Fifth Century--the Elephantine Temple was destroyed; and the Ark was removed to Lake Tana in Ethopia. The rest of the story tracks Ethopian history to Aksum.
Jewish belief is that the Ark will reappear at the time the Messiah enters Jerusalem. Maybe the Anti Christ will use the Ark to support his claim; alternatively, maybe tradition is correct and the Ark won't appear until the Lord returns.