We set up the SSL Certificate Sensor on an Exchange server where it found an old expired self signed certificate. It gave an alert as expected. On the server in question we then created a new self signed certificate and deleted the old one. The sensor in the PRTG is still alerting us about the old certificate even though it doesn't exist anymore. We tried to delete the sensor and add it again, but for some reason the original error regarding the expired certificate shows up again.
Why is that and how do we fix it?