Please ensure that you have logged in to Journey with the Google Account that you used to purchase the premium upgrade. Otherwise, your account would be on the free version and not the premium one.
If it still does not work, ensure that you remove any and all other Google Accounts on your Google Play Store that you did not use to purchase the premium upgrade. After which reinstall Journey and see if it works.
Please note that your Premium upgrade is for only 1 copy of the premium version on 1 Google Account only.
Also see Restoring purchase