Delete the sensor, and swap the battery with a new one from a known working sensor. Then Relearn the sensor from its installation location. When auto enrolling, hold the internal enroll button down until the LED lights up, then immediately let go. Does the sensor Auto Enroll?
If not, how far away from the panel is the sensor and what material is the sensor mounted on?
In general, when learning in wireless sensors, unless specifically stated, use the Auto Learn function over manual. This ensures that the sensor communicates to the panel
Additionally, there is a newer firmware version for your panel, 2.6.0. Its currently only upgradeable via patch tag, steps and patch notes found here.