Please check if this steps help reactivating your access to the pro version: https://help.orrs.de/1256/troubleshooting-pro-version-activation-via-google-play?show=1256#q1256
If they do help, please go to the about section of the app (three bars at the top left of the main list --> three dots --> About) and press on the "Pro-Version" field. There you'll find a share button in the action bar - just choose your favorite email app and add a note to the text referring to this help text so I can extend the subscription as reimbursement.
If it doesn't help, I can only offer you a refund as it would be a bug in the Google Play licensing system and I have no control over it. For that, please just forward the Google Play receipt you received via email to firstname.lastname@example.org
Sorry for the inconvenience!