They work perfectly fine... Look at your gems not the acquired gem... Mine went up from 3,650 to 43,000 in no time. The reward screen doesn't show you get the rewards but you do receive it...
Not all mods are made the same.
Most of the time A12+ Or xiaomi/realme has issue with mod and for that please use Virtual App such as x8sandbox, vmos etc
Confirmed working on NoxPlayer A9.