A month ago I bought an ASUS Zenfone 8.
It has worked flawlessly so far.
I have now run into a problem: I cannot choose my own notification sound.
When I press the big "+"
and select the mp3 file I want to import/use 
and then press "VÆLG"/SELECT 
the phone returns to the audio selection screen, but my selected/imported mp3 file cannot be found.
I had no problem importing my own ringtone.
It went without any problems.
What do I do wrong?
Data about my phone:
Model: ASUS Zenfone 8