This is a known bug in the current app version that can cause an active subscription to incorrectly appear as expired. An update with a fix will be available very soon.
In the meantime, you can usually restore access right away by following these steps:
Delete the app from your device
Reinstall it from the App Store or Google Play
Open the app and sign in with the same account you originally subscribed with
In most cases, access is restored immediately after signing in again.
If the issue persists after reinstalling, コンタクトサポート and include the email address used for your subscription.