Please follow this procedure if Smart Launcher can’t verify your license and if you are using more than a Google account on your device.
Uninstall Smart Launcher, if you want you can perform a backup to avoid losing your configuration.
Using a computer open this page https://play.google.com/store/apps/details?id=ginlemon.flowerfree and log in using the same account you used to purchase the license.
Click on “Install” in the web page, then wait the install process to finish on your device.
After the installation check if Smart Launcher recognized your license. If it doesn’t a reboot could be necessary.
Since the issue causing this problem is related to how Google Play Store handles purchases in a multi-account environment, this procedure could help even if you’re experiencing the same problem with another app. Let us if the procedure helped you in our community.