Contact sensor continues to show tampered in app

I had a contact sensor go off offline in my app. In an attempt to check the sensor I pulled off the cover and got a tampered indicator for the sensor. I 've tried to reset it numerous times from the sensor by removing the cover, removing the battery, pressing the tamper button and replacing the battery as I hold it in. After the flashing finishes, I replace the cover but continue to show the tampered indicator in my app for that sensor. What am I doing wrong?