I know this is a old thread but it's still relevant.
If you have a Minix Neo TV box and want DStv now, you need to download version 1.40.6 (
https://m.apkpure.com/dstv-now/com.dstvmobile.android/download/213014006-APK?from=details/version) this version won't give you the Google certificate error. Don't use the latest versions.
If when installed it says your device is already registered on another account go to DSTV live chat, give them your DStv credentials and your device ID (on the app go to settings-manage devices to see device ID). They will tell you it's been successfully deregistered and you may now register it on your device.
Go back o the DStv now app, settings - manage devices and register your device.
Sorted, you now have a working DSTV now app on your Minix Neo.