To transfer your playlists or favorites albums, tracks, and favorites from one service to another, we need API access to "write" this information in your music account.
Unfortunately, some developers' access (API) does not allow us to add such types of elements to the user account.
That's why, while using Soundiiz, you can have some elements not transferable to the destination service. We recommend you check this compatibility page to know precisely what elements can be retrieved from a service and what features can be added to that service too.