Keypads won't register new devices even though devices are detected by base

If you have the interactive monitoring plan, you can add them through your online control panel, and name them as well (in the Devices section).  I believe that this method also requires, however, that you still have to press the sensor button to "pair" it (when I did it this way a couple years ago, there was a popup prompt that required the sensors/components have the button pressed, you'd press it, then the popup would disappear so you could finish entering it in Devices) - be sure to click "save changes" when done.

@hsg_1 However, the sensors are being detected since when I open a door or separate the magnet from the entry sensor, I get the chime. - well that would indicate that your sensors are already installed (this is normally done before the system is shipped) and you can't install the sensors twice.