Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
The main condition for praying, fasting, making Tawaf around the Ka'abah etc. is being in a state of ritual purity. A woman having her period is considered in a state of ritual impurity; so she is forbidden from performing such obligations during her menses.
Allah knows best.