Hi @lakeguy77! If your Range Extender is plugged in and setup to the Base Station, this device should connect with your Contact Sensor depending on placement. The best test will be to eliminate the Range Extender from the area, and bring the Contact Sensor in question closer to your Base Station. Once done, please attempt a few open/ close events and allow some time for the Ring app to display the updated signal strength. The Contact Sensor should have it's strongest connection near the Base Station. This will confirm that your Contact Sensor is reporting proper statuses.
Something else that can be done, is moving a different Contact Sensor to the desired mounting area where the signal concern is, to see if another Contact Sensor displays a different signal strength.
Often times, if the Base Station is within reasonable range of a sensor, the sensor will remain connected to the Base Station rather than using a nearby Range Extender. If this is so, and the Contact Sensor is operating as intended other than utilizing the Range Extender, this will mean that, for the time being, the Base Station is providing the better connection. Rest assured, if the Range Extender is needed for communication, it will be used. I hope this helps!