Hmm, you should be able to play your downloads while in Offline Mode. Could you share a short screen recording which shows the app's behavior in action? That way we can get a clear understanding of what's happening on your end.
It's worth reinstalling the app by following the steps here, in case you haven't already. If possible, try logging in to another device, download your music there and set the app to Offline Mode to see if there's a difference.
Keep us posted on this. Cheers!
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