I hope that this post helped to identify your problem. As far as I can tell, the battery provides the basic functionality that it's supposed to now (charges up and keep the phone working when the power is off). But when it's working properly it is supposed to indicate whether or not the battery is connected and working properly (i.e., not worn out). It seems very weird that they would disable that feature.
I have put my modem on a UPS now so that my internet keeps going when the power goes out as well as the phone, so the built-in battery is not as important as it used to be.
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