Offline stations are regularly deleting themselves. Unless there are licensing restrictions that Pandora isn’t sharing, the only time a downloaded station should delete is when I initiate. What’s going on with this bug?
Thanks for reaching out and sorry to hear some of your offline content is disappearing.
If your offline content is missing due to a licensing restriction, the song will be labeled as "Radio Only" or be unavailable, which could be one of the reasons why some of your offline content are missing.
If it is not labeled as "Radio Only", I'd recommend signing out of the app and signing back in, which will reset the download process. Then, make sure to keep Pandora in the foreground of your device while the download completes.
If you continue to have trouble, check the download icon for the content you are attempting to download. The two rotating arrows indicate that the content is still in the download process and the highlighted downward pointing arrow means the content has successfully downloaded.
If the icon is not highlighted, try downloading the content again and keep the app in the foreground while the offline music downloads. Keep in mind that stations and large playlists take a longer time to download.
If you are having trouble downloading stations, try downloading a single track for offline listening to see if that works.
Lastly, I'd recommend that you perform our iOS Troubleshooting Steps. However, Pandora Premium and Premium Family listeners may need to re-download some of their offline content after reinstalling the app.