Did you take an apk file from somewhere else? There are android versions made by other people elsewhere that don't work to update my official game version.
Not sure of the colon matters, since I usually test if the new apk file works by updating the game on my phone. But I can't make new apk files anyway at the moment, so there is not much I could do either way until I fix that issue. :(
downloaded the APK straight from https://sensitiveusername.blogspot.com/2019/09/renryuu-ascension-v190920smoother...
I guess the only chance to keep my save data is wait for the next update and cross my fingers it updates correctly or root my OS. I'll see if there's a way to extract the save data