Hello,
I use the Razer Deathadder Chroma 2014 so I am familiar with Razer synapse. Firstly, try using different USB ports, trying to get the basic troubleshooting out of the way. If you've tried all of the USB ports and it still isn't recognizing it restart your PC, and try again. Once it is confirmed that it isn't an issue of what USB slot you are using try uninstalling and reinstalling the Synapse.
1. Uninstall Razer Synapse and delete all the files in C:\Program Files (x86)\Razer and C:\ProgramData\Razer. You must reveal hidden files/folders to do this.
2. Restart PC
3. Open Device Manager. Go to Keyboards, Mice, and Audio and uninstall ALL HID Keyboard, mouse drivers, and all other Razer product drivers. Be sure to select delete drivers when uninstalling.
4. Restart PC
5. Turn off fireall/antivirus. Download the latest Razer Synapse installer from their website (do not use an older installer). Make sure you do this instead of trying to install another way.
Synapse should now recognize your devices.
If still not working make sure you have a legitimate Razer device.
Hope it works