where did facebook messenger "ding" sound go?

one day i wake up and i have no sound for facebook messenger notification . so i go into the sounds and the messenger "ding" sound option is gone .
theres other sound options but i want the "ding " back . my wifes phone still has it (same exact phone) i dont understand

also how can i add this sound? i downloaded the sound file but cant add it ,i tried putting it in various folders but none added it to the choices of sounds for messenger notification sounds .

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