Brian wrote:
The UPS then worked normally! So yes, as the early responders answered,
it was simply dead batteries. Will recycle the old ones, and keep the
UPS plugged-in continuously so that hopefully these new batteries will
last a long time.

Keep an eye on that thing. DO google the SmartUPS 700 for experience stories.
If the batteries ever significantly discharge (i.e. more than a few minutes
off mains), I highly recommend you put new ones in rather than trust the
used ones, based on my experience. Mine is off line and scheduled for
destruction and recycling.

--
And no, no one can have it. You'd sue me when it goes bad again.