When you have a mobile device, such as a smart phone or tablet device, you use an ACCOUNT with this device to sign into the app store on the device so that you can install apps.
This is true for both Android (Google) and iOS (Apple) devices.
As with all apps, when you purchase an app, the app is purchased by the app store ACCOUNT used at the time of purchase, not the device the purchase is made on.
After purchase, the app is attached to that account "forever".
If you want to install a purchased app (this applies to any app, not just Hema's) on a new device, the device should be signed into the same app store account which owns the app.
If you want to install the app on multiple devices, they should be signed into the same app store account which owns the app.
On an iOS device, when you go into the iTunes app store and find the app, you should see a little cloud icon with a downward pointing arrow, indicating that the current app store account owns that app, which means you can install the app without paying for it again. See
Apple's article here for more details.
On an Android device, when you go into the Play Store and find the app, you should see an INSTALL button, indicating that the current app store account owns that app, which means you can install the app without paying for it again.
You can also use Family Sharing to share purchased apps across family members using devices with different accounts.
If you want to use Family Sharing, try using Google Search to search for information related to Family Sharing on the app store platform you are using (Google - Android or Apple - iOS).
You cannot install an app from one platform's app store on another device which uses another platform.
So, you cannot install an app purchased on an Apple iOS device on an Android device, and vice-versa.
Changing platforms requires you to purchase the app in the app store for that platform.
If there are issues with your app store account, we cannot assist with this, as your app store account is managed by the relevant platform owner (Apple or Google). You would need to contact the relevant support department for the device platform you are using.
With regard to the Hema Explorer Pro subscription used in conjunction with the Hema Explorer app (not used with the Hema 4WD Maps app), that is attached to your Hema Explorer Cloud account (this is a separate account - not related to your app store account).
So, if you have multiple devices, and they are signed into the same Hema Explorer Cloud account which has the Pro subscription attached, they will all get access to the Pro content. It doesn't matter if they are all Android devices, all iOS devices, or a mixture of both.