Bought a new whisperer as an old one is no longer working.

REMARK : WHILE I LIVE IN A TEMPERATE AREA NONE OF MY WHISPERERS LASTS MORE THAN 26 MONTHS WHICH IS SURPRISING AS IT IS NOT SUPPOSED TO BE A CONSUMABLE.

Clicked as required first blinking blue light then blinking white light.

Went to sensors and see the dead old one, the working one but do not see the newly bought one.

Do not see either a + sign to add a new one.

What should I do ?

Any way for end user to open and replace battery on a whisperer 2?  It is out of warranty.