Hi crooky!
You've done nothing wrong and installing the newer version over the old one is the right way to update the game while keeping your save.
But, like everything else in computing, sometimes it seems that we run into some errors that doesn't make sense, and this time would be no different.
During our testing phase of the game on Android, this update process went well 95% of the time, but there were 2 occurrences in particular that sometimes caused the installation to fail, here they are:
1) This is the most common: Insufficient space - It may be that your mobile is almost full and therefore cannot complete the installation.
In that case, we recommend deleting things you no longer need to keep on your mobile to free up space and try again.
2) If you freed up space and still couldn't install it, it may be a bug in the apk installer app.
This has occurred to us a few times, so it might be interesting to try installing again a few times or even trying to use another apk installer app.
You can also perform a clean install, deleting v0.1.4 and installing v0.2.4, but you may lose your save when doing this, so do it at your own risk.
We hope these tips can solve the problem.
Thanks for your support! ^^