Once you have purchased a sound pack or Pro Feature individually, you should always be able to access them within the app.
As in-app purchases cannot be transferred between Apple IDs, if you have lost access to a sound pack or feature within the app, please check that you are logged into the same Apple ID that you used to purchase the sound pack or feature.
You can check you are signed into the correct Apple ID by checking your purchase history. Please see this Apple support article on how to check your purchase history: https://support.apple.com/en-gb/HT204088
If a sound pack or feature is not installed on your device Launchpad, Blocs Wave and Groovebox all have a 'restore' function, which will reinstall the sound pack or feature on your device:
In some cases when you’ve switched Apple ID accounts on a device, your purchased sound packs or Pro features may not appear in the restore list. To resolve this, make sure you are signed into the correct Apple ID and re-purchase one of the sound packs or Pro features you’ve already bought. This will refresh your purchase receipt and all of your missing purchases will become available to you again. You will not be charged twice for this if you are signed into the same Apple ID you originally made the purchase with.
If you are a Launchpad Premium user and have lost access to features or sound packs, this may be because your Launchpad Premium subscription has expired or you are not signed into the same Apple ID the subscription is associated with.
It is also worth noting that changing your App Store region may make purchased features unavailable.