It is mainly caused by an old version of "Android System WebView" if your device is Android 5.0 and above.
Reasily relies on it to display epub content. So you have to keep it updated in Google Play Store.
If your device is Android 7.0 and above, please update the Google Chrome app instead.
If the night mode still not works, please mail me the epub file with a screenshot, so I can find out the cause of the problem.
Please check if the same account is logged in when enabling "Auto-sync data" or clicking "Sync now" on all your devices. You can "Log out" to change the account.
Make sure the internet connection is stable, then click "Sync now" to make it sync again. If the syncing message disappeared automatically, the data is synced successfully.
Please also check if the epub files are not different versions of a book on your devices. Data will not be synced between different versions of a book.
You can enable the "debug log" and "mail me" it so that I can check if there are some failures during synchronization.
Some Reasily Pro users have reported that Reasily asks them to upgrade again.
This usually happens on your second device.
It is possible that Google Play on your second device hasn't updated the purchase state yet, so you could try: Clear memory, reopen the Play store to let it refresh purchase state. You can also try rebooting the device. Make sure the internet connection is stable.
If you have multiple Google account, the app should be installed with the account paying for pro before. That is, the account should be selected in drawer menu of Google Play when installing Reasily. Otherwise, Google Play thinks Reasily is owned by another account and is not paid. You can check whether the correct account is associated to Reasily by clicking the "Donate" in the menu. You might have to uninstall and install Reasily again with the correct account if the current associated account is incorrect.
If it is still not working, please tell me. I can refund money or give you a redeem…