I have a Samsung S7 for which I bought a 200GB microSD card. I formatted it as adoptable storage (using an adb shell workaround because Samsung has actually disabled the Marshmallow feature by default). Now, I can store all manner of things on it, including about 17GB of music which I manually copied over.
However, I want to use DoubleTwist Sync as I have lots of iTunes playlists that don't get copied over when manually copying files. I installed both the DoubleTwist PC app as well as the Android app but when I tried to sync, it just tells me that the device is out of space. I know that this isn't technically true as it's a brand new card and I just copied over 17GB of files. In fact, when I deleted the 17GB, it still told me that there's no space. I'm sure the problem is that DoubleTwist can only see a limited partition and it is somehow confused by adoptable storage.
There's an article on their site (https://www.doubletwist.com/help/question/how-do-i-switch-from-internal-storage-to-sd-card/) describing how to switch from internal to SD storage, but I think it was written without adoptable storage in mind, as my Settings doesn't have the "Storage" option they refer to.
Any ideas on how I can fix this? My last resort is to re-format the card as 50% adoptable storage partition and 50% portable storage partition. To be honest, I probably should've done this from the get go but I'm hoping there is a quicker solution that doesn't involve reformatting.