Try connecting into different port (at least USB 3.0 directly into motherboard).

Try removing all drivers and synapse:
Uninstall Synapse
Download & run this tool: https://rzr.to/Tf53xj to remove any razer drivers/leftovers
Then restart your PC
After reboot install Synapse again (as administrator).

Also you can try the mouse without synapse on other PC.

I'm sorry, I did everything you said, but it still didn't work, the green dpi light is still flashing under the mouse.

So you can only warranty return it.

You can also try contacting Razer Support directly: https://mysupport.razer.com/app/warranty-support/

Okay, it sounds good, it's under warranty. The mouse broke without me doing anything. Actually, we can exchange it instead of returning it.

So how do I return or exchange?

I wrote to Razer support, I hope they can help, but as I said, I didn't do anything, while I was playing a game, it suddenly went away and the dpi light is blinking, only the sensor light is on.

So how do I return or exchange?

I always return to the shop, where I bought it. So if you’ve ordered it via Amazon for example, then I’d contact Amazon, but since you’ve already wrote to Razer Support, just wait for their response.

Me too, I think firmware reset after updating, Razer viper 8KHz same issue, but this problem solved only restart motherboard mouse or use programmer, refirmware

looks like i have same problem. dpi button doesnt work on click. always red. But 5 seconds push changes hz its blinking