There is a mosque in Taj Mahal and that is still active mosque and on every Fridays Taj Mahal is opened only for the worshippers and for the others it remains closed which is why there is no train and no tour on Fridays and that's why all fridays are blocked...
You can't visit Taj Mahal any Friday because it is only open for the muslims.
Friday is a holy day for Muslims.
I hit the wrong arrow and meant to upvote Betrina who is absolutely correct!!!!