5268ac Gateway Wouldn't Re-Set

I have a 5268ac gateway with internal battery back-up.  When it seemed to be 'stuck' (i.e. no internet, TV or phone even though its lights were ON), I usually just press the Re-Set button for a re-boot, and all returns to normal.  This time, the re-set button would NOT re-set the gateway, and even if I un-plugged the gateway, it wouldn't re-boot, and its lights kept showing green.  I had to physically remove the internal battery before it would re-boot. Why didn't the re-set button function?  Do I have a faulty 5268ac or a faulty internal battery?