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