How is the missed Maghrib prayer performed after the Isha call to prayer?

Whoever misses a prayer due to sleep or forgetfulness, must make it up immediately upon remembering it, for the Prophet, peace and blessings be upon him, said: "Whoever forgets a prayer or sleeps through it, its expiation is to pray it when he remembers it."

If you remember a missed Maghrib prayer and there is ample time for the 'Isha prayer, it is better to pray Maghrib first, then 'Isha, in observance of the obligation of sequence.

However, if you pray 'Isha first with the congregation and then make up Maghrib, there is no harm, as the issue is subject to scholarly disagreement, and the preponderant view is that sequencing between missed prayers is not obligatory, which is the view of the Shafi'is.

If the time for the present prayer is short, one should begin with the present prayer then the missed one. If the time is ample, it is preferable to begin with the missed prayer then the present one, but if one begins with the present prayer first, it is valid.