If I recall, in the 16 it’s a combination of the EC and the QMK firmware in the keyboard turning off the blacklight for sleep. Input modules have a SLEEP pin that current EC firmware uses to turn off lighting during sleep, though there has been some talk about using it to send lid closed status. [RESPONDED] Waking from suspend w/ lid closed - #13 by Kieran_Levin
So for this, the backlight not coming back on after sleep, the fault could be with the EC failing to turn off the sleep pin or QMK not responding to it, if it’s even programmed to come back automatically, I don’t know.
Do they respond to the hot key to turn them on, or are they stuck off?