I can’t play downloaded songs when offline signed out Apple Music downloaded all again still

Probable you are not downloading properly on your device.

Add music to iPhone and listen offline

1. Touch and hold a song, album, playlist, or video, then tap Add to Library.
2. When viewing the contents of an album or playlist, tap near the top of the screen to add the album or playlist, or tap , then tap Add to Library to add individual songs.

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Add music to iPhone and listen offline - Apple Support

i have downloaded properly but still its acting like im streaming the music when i have downloaded the songs.