The POCO M5s is a MediaTek (MTK) device. If your phone is completely dead (won't turn on, no charging icon) but is recognized by the PC as a or "Preloader" for a split second when plugged in, it is likely "Soft Bricked" and can be saved using the SP Flash Tool method below.
There is no key combo guaranteed. Instead, use the (hardware-level): how to unbrick poco m5s
