Thermostat LR-HWLV-HVAC: how to check whether it is defective or not?

Hi guys,
I tried to install Lutron Honywell TouchPro Thermostat LR-HWLV-HVAC and couldn't get the display to turn on. I have the battery installed too. The battery is good and I can measure 3V DC voltage from the CR2032 battery. I have all 5 wires (red, green, yellow, white and blue) connected. Blue is connected to "C" (Common). R and Rc is connected by a jumper.

The original thermostat only uses 4 wires (red, green, yellow, while) and the R and Rc is connected using a jumper.
From the wall I have 2 extra wires (blue and purple). There is about 22v AC voltage when I measure voltage between red and blue. I assume blue is the common in this case, right?

What is the easiest way to check whether the thermostat is defective or not?

Thanks all.

Looks like short of having a transformer or power supply with 24V AC output we have to really install it to check whether it is working or not. The lithium battery is ONLY used to keep the date and time data not used to power the LCD display.