But never did their faith benefit them once they saw Our punishment. (40:85)

﴿فَلَمْ يَكُ يَنفَعُهُمْ إِيمَانُهُمْ لَمَّا رَأَوْا بَأْسَنَا ۖ سُنَّتَ اللَّهِ الَّتِي قَدْ خَلَتْ فِي عِبَادِهِ ۖ وَخَسِرَ هُنَالِكَ الْكَافِرُونَ﴾
[ غافر: 85]

40:85 But never did their faith benefit them once they saw Our punishment. [It is] the established way of Allah which has preceded among His servants. And the disbelievers thereupon lost [all].

So their bringing faith upon seeing the punishment descending upon them, did not benefit them.
This is the way of Allah that has been consistent among His servants: that their bringing faith upon seeing the punishment is of no use.
The disbelievers doomed themselves at the time when the punishment descended, by having put themselves in a place of destruction because of their disbelief in Allah and not repenting from it before seeing the punishment.

Then their Faith (in Islamic Monotheism) could not avail them when they saw Our punishment. (Like) this has been the way of Allah in dealing with His slaves. And there the disbelievers lost utterly (when Our Torment covered them).

phonetic Transliteration

Falam yaku yanfaAAuhum eemanuhum lamma raaw basana sunnata Allahi allatee qad khalat fee AAibadihi wakhasira hunalika alkafiroona

Abdullah Yusuf Ali - Translation

But their professing the Faith when they (actually) saw Our Punishment was not going to profit them. (Such has been) Allah's Way of dealing with His Servants (from the most ancient times). And even thus did the Rejecters of Allah perish (utterly)!

Safi-ur-Rahman al-Mubarakpuri

Then their Faith could not avail them when they saw Our punishment. (Like) this has been the way of Allah in dealing with His servants. And there the disbelievers lost utterly.

Page 476 English transliteration