Hii there was a glitch in the data base but basically your list is still there but you won’t be able to see it. They’re fixing it based on the date you added the manga (like you’ll see a manga you added to your list in 2020 earlier than if you added it in 2024). So far only the mangas you’ve rated came back but I think they’re still fixing it? It’s just gonna take a while. I think it’s been going on for a few days (maybe a week?).
(This is just what I gathered from reading other comments, there’s a link to FAQs further in the comments that’ll provide more details)

I opened my mangago account in the pandamic you can imagine how big of a collection I freaking had !!!! I didn't even notice when my account went clean as white sheet wtf ??? where are all my lists , all the mangas and manhwas I wanted to reread and barely remember their titles is this a glitch ????? pls tell me it is and maybe my things will come back ...did something happen when I wasn't here ????