According to the story, the guards noticed them and prevented them from entering.
They claim that "settlers" have repeatedly attempted to sneak in to the Temple Mount in recent years, particularly in times of Islamic prayer when it is crowded with worshipers.
I have no idea if any of this is true. The closest story I was able to find was this one from last year, and the Jews were secular:
Two Jewish youths were taken in for questioning by Jerusalem police after attempting to enter the Temple Mount dressed as Muslim worshippers.
According to initial reports the pair are "secular Jews" who were touring Jerusalem together and wanted to include the Temple Mount on their trip; it is not clear why they chose to disguise themselves.
UPDATE: It seems possible that the Al Aqsa Heritage Foundation fell for a Purim joke from Arutz-7:
A group of Temple Mount activists were spotted dressed up as Arabs on Friday in order to be able to enter the compound.
The Jewish activists did not do this in the spirit of Purim, which was celebrated in the capital on Friday. They did it in order to get around a ban on Jewish prayer which was imposed by the police.
Despite a court ruling earlier this week which said that police “must make sure that Jews are able to pray on the Temple Mount”, officers have been restricting Jewish prayer at the compound since Wednesday, telling worshippers that the restrictions are in accordance with a decision by the political leadership following pressure from Jordan.
On Friday, Jews who wanted to visit the Temple Mount were told by officers that on Fridays the Temple Mount must be free of Jews regularly, even on Purim.
The worshippers who were forced to dress up as Arabs said, "It is inconceivable that we cannot be on the Temple Mount on a day like today.”