How to fix iTunes playlist issues on iPhone 15 without Wi-Fi?

iphone 15, ios 18. took a flight last week and tried to shuffle my playlist or just play my whole playlist .. would not work without wifi it said.. but i have downloaded all my songs on my phone and ipad always but no matter what i try i cannot get my playlist to play .. i can click on them one by one and they play ok .. but playlists in total will not play. ( i do not subscribe to apple music) but all my songs are downloaded and paid from itunes..

seems to be an IOS 18 issue as last year they played fine.

anyone got a solution or know when apple is going to fixed this

[Re-Titled by Moderator]

Original Title: playlist when no wifi