Hi there! I understand you're having trouble turning your DayBand device off and on, and you're seeing a green light blinking constantly on the back. Let's work through this together.

First, just to clarify:
1. When you try to power the device off or on via the DayBand app, does it respond at all?
2. Have you tried any physical buttons on the device itself to power it off?
3. Is the green blinking light continuous, or does it blink in a pattern (e.g., a few times then pause)?

Meanwhile, here are some initial steps we can try to resolve the blinking green light and power issue:

### Step 1: Disable Wrist Detection (if applicable)
Sometimes, the green light is the heart-rate sensor’s LED trying to monitor continuously due to wrist detection being active, which can keep the device 'awake.' On your band, go to Settings > Security and try disabling the wrist detection feature. This can often stop the green light and may allow the device to behave normally2.

### Step 2: Force Restart the Device
If the device isn’t responding, try a forced restart. Usually, you press and hold the power or multifunction button for about 10-15 seconds until it powers off and restarts. If your device has multiple buttons, try holding the main button alone or in combination as per your model's manual.

### Step 3: Reset the Device to Factory Settings
If the above steps don’t help and the green light continues blinking nonstop, performing a reset to factory settings may clear any software glitches causing the issue. Be aware this will erase any data not synced to the app. To do this, typically:
- Go into the DayBand app on your Windows device,
- Find the device settings,
- Look for the option to reset or restore factory settings,
- Follow the prompts to complete the reset3.

### Step 4: Check Battery and Charging
A blinking green light can sometimes indicate the battery is low or there’s a charging issue. Ensure your device is fully charged using the original charger, and see if the blinking persists or stops after a full charge.

Please try these steps and let me know what happens at each stage. If nothing changes, do let me know the exact device model and any recent changes before this issue began.

Are you okay to try this?