Here's a quick fix.
First, please make sure you are using the same Apple ID or email address you used for the purchase.
Next, try the following steps:
1. Open the Hashtag Expert app. Now tap the Profile tab at the bottom right corner of the app.
2. Next, tap the gear button.
3. Tap Membership.
4. Tap Restore Purchase.
You may need to restart the app and sometimes you may need to also restart your phone as well.