Please ensure that:
If the issue still persist, you can use the following workaround.
Delete the data and cache from the Google Play Store app.
Go to “Settings” on Android device > App Manager
Find the Google Play Store app in the list and bring up the info page for it.
Here you can delete the app data and empty the app cache, then restart the Android device before opening Music Maker JAM again.
After performing these steps, the list of purchased Mix Packs (which are connected to the currentled logged Google Play Store user accoun) can be seen in the “Mix Packs” section under ‘My Music’.
If the packs are still not listed, we request you to kindly wait for packs to finish downloading completely onto your device before coneacting our support team.