Praise be to Allah.
You should urge the brothers around you to attend Salaat al-Jumu’ah (Friday prayers) at the right time, because Jumu’ah is of great importance. The Prophet (peace and blessings of Allaah be upon him) said: “Let people stop neglecting to attend Jumu’ah, or else Allaah will seal their hearts, then they will be among the heedless.”(Reported by Muslim, 1432)
He (peace and blessings of Allaah be upon him) also said: “Whoever neglects Salaat al-Jumu’ah three times with no good reason, Allaah will put a seal on his heart.”(Reported by al-Tirmidhi, 460; he said: this is a hasan hadeeth).
As for the people who missed Jumu’ah, they should pray Zuhr, and there is nothing wrong with praying it in jamaa’ah (congregation). And Allaah knows best.