A. Restore your mouse settings:

Open Pulsar Fusion Software, in the button assignment tab, click on "Restore"
This will put your settings back to default.

B. Re-install your firmware:

1 - Go to pulsar.gg/pages/download
2 - Select your mouse model

3 - Click on "Firmware"

4 - Download the file

5 - Plug your mouse in

6 - Run the program