I used custom hitsounds on my Amphibia beatmap and none of them play. I already put them in the Beatmap folder and played the map in the editior. I had the correct names and were formatted as .wav, I only heard my skin's hitsounds. Next time I selected the default skin, and still had the standard hitsounds.
Map Link >> https://osu.ppy.sh/beatmapsets/1794297#osu/3677426
Map Link >> https://osu.ppy.sh/beatmapsets/1794297#osu/3677426