1. Make sure GWENT: Rogue Mage is updated, this article explains how to update apps: https://support.google.com/googleplay/answer/113412?hl=en
2. Make sure your Android version is up to date, here's how: support.google.com/android/answer/7680439?hl=en
3. Try updating Google Play Services and Google Play Store, here's how: support.google.com/googleplay/answer/113412?hl=en
4. Clear cache and data of GWENT: Rogue Mage:
• On your Android device, open the Settings app.
• Tap Apps & notifications and then See all apps.
• Scroll down and tap GWENT: Rogue Mage.
• Tap Storage and then Clear Cache.
• Tap Manage Space and then Clear all Data.
WARNING: Clear Data, as well as uninstalling the game will delete your save files in GWENT: Rogue Mage.
5. Clear cache and data of Google Play Services & Store in the device's Settings app. Refer to the steps 2 & 3 here: https://support.google.com/googleplay/answer/9037938?hl=en
6. Restart your device.
7. Try uninstalling and re-installing the game.