If you have purchased a new HS510C and you are seeing symptoms such as the the reticle not turning on, blinking, or other odd behaviour, there is a simple solution.   

The HS510C contains a super capacitor.   It allows the sight to function even in the dark for several hours without a battery.   If the sight has been stored without a battery for a period of time, the super capacitor can become discharged.   Please place the HS510C in sunlight or bright artificial light for a couple of hours.    This should address the issue.