This seems to be a problem for a lot of people. Some things to try:
1. Make sure you're on Android 8.0+
2. Ensure you have at least 270MB free
3. Try restarting your device
4. Try clearing your device's cache
5. If you have a second Android device you could try downloading the mod on it and see if it works.
If you still can't get it to work I'll be willing to help you further.