Some advancements such as ride a strider and hit center of bullseye will not show up once ive done them.
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@galaxy_2Alex The advancement lists 30 m away and i was 31... My friend was able to get the advancement from the same spot

See MC-184271, Mojang is unable to reproduce this either.
The strider one is MC-183764, as for Bullseye, please make sure you are 50 blocks away at least.