There may be many reasons why you're having problems downloading the game, so please refer to the following.
1. Insufficient capacity of the device
For iOS, approximately 140MB and 55MB of additional resources are installed and for AOS approximately 136MB and 45MB of additional resources will be installed on the device.
If the minimum space for installing the application is not secured, downloading is not possible.
Please make sure to secure enough free space. (Recommended free capacity: about 1.6 GB, as of August 2021)
2. Poor data communication
If the remaining data communication capacity of the device being used is insufficient or data transmission/reception is interrupted due to poor communication environment, downloading may be difficult. Please download while using a stable Wi-fi connection, and be careful not to run out of data capacity when using data.