What is the ruling if the Imam's voice cuts off, so the worshiper intends to pray individually and completes one raka'ah, then the voice returns; is it permissible for him to rejoin the Imam in congregational prayer once again?

If the Imam's voice cuts off during prayer and the worshipper despairs of its return, it is permissible for him to separate and complete his prayer individually.

If this happens during the Friday prayer, then if the worshipper caught one rak'ah with the Imam, he completes it as Friday prayer. But if it happened in the first rak'ah, he completes it as Dhuhr prayer.

If the Imam's voice returns after the intention to pray individually, the worshipper has a choice: either to return to follow the Imam or to complete his prayer individually. If he returns, and his prayer has advanced beyond the Imam's, then he sits for the tashahhud and gives the salutation upon completing his prayer, or he waits for the Imam to give the salutation with him.