I had something similar happen yesterday, while I was waiting for my car to be repaired, I played a few levels on mobile data, then suddenly the game won’t connect and it kept asking me to check my internet connection, and then when it finally connected again, it was trying to download some packets at the loading screen, except mine was 1533 or something and kept booting me out.
I restarted my device and tried to connect again, it did and was slowly crawling along the same packets to download. My phone is already running low and not wanting to waste any more juice seeing this excruciatingly slow and painful process, and needing my phone in case the car repairs are done, I just turned off the app.
I waited until I got home, put the phone on the charger, connect to home WiFi before trying again. The packets were downloaded more swimmingly and the game was running normal after. Not sure if this big download was some feature enabling contents down the road (like when to release Yunan / Rana costumes into HA10, don’t quote me on that, I am just guessing).