If it is via the App Store or Google Play Store, please go to the Premium page in TickTick, scroll down to the bottom and tap the Restore button, check if it is activated.
If that does not show you Premium features, please sign out and back into your mobile app. If, after that, you are still not seeing them, please contact us with your registered email address and the platform you made the purchase, we will make sure you get access to them right away.
If it is via PayPal, could you please provide us your registered email address and the transaction payment screenshot? We will check it on our end.
If you have any other specific questions or concerns, please send us feedback within TickTick apps. To send us feedback, for mobile apps, please go to Settings > Feedback & Suggestions; for desktop apps, please go to Avatar > Feedback.