Hello, I have an issue with all of my downloaded songs

I have a premium account and I downloaded all my 2000 songs so that I can listen to them on "offline mode"

But today, without any explanations, all my songs are not available anymore, the green arrow near every music, the one which shows you that your song is available offline, is now grey. Therefore, I can't listen to them anymore if I don't download them again ...

BUT, I also have a HUGE problem ! Not only my songs are not available anymore and I have to download them again, but all the previous songs are not deleted either !! Because the size of the app remains the same ! And when I download them again (sadly), the size taken by Spotify keeps growing

This means that all my songs are gone, I can't listen to them anymore but I still have 8GB of music on my app. And when I start to download them, Spotify add all the songs to the previous 8GB ... How is it even possible ??