Settings: My phone stopped detecting custom notification sounds (but are the custom ringtone sounds still working?)

I installed some custom notification sounds on my Android a few months ago and they worked fine for quite a long time until, recently, all the sounds of my notifications returned to the default values, so I try to switch back to any of the old ones Custom sounds that you had been using will not appear in the options
My custom ringtone sounds did not change and they still work fine, but my notification is not displayed. I tried to restart, changing the location of the files, erasing the cache, but nothing works anymore. it's getting really annoying klsdnklvnskldn