It isa problem with Android 6.0, AKA MarshmallowI have the same device under Boost Mobile, which sernt out an OTA upgrade to Nougat around 2 years ago. Although you won't be able to move the entire app to the card, as a small portion needs to remain in internal storage for the app to work, the data portion will be moved, freeing up space. For anyone who might be on Sprint, Boost or Virgin Mobile, the update may already be there. Open up Settings,then General, scroll down to System Updates and the file should be there. If not there, go to the Website and there should be a list. If not, google it. The SD card will appear in Storage and movable apps will have a change button. In addition, there will be the option of a dark, high-contrast display background, improvements in battery life and security.