cannot activate software for my headset

So a few months ago , i somehow couldn't use the software that i installed for my razer headset (Electra V2)(& the software was the razer synapse that supported headsets) and i got logged out and couldn't use it again because i needed to activate it with an activation code that i couldn't find on the box , I've looked everywhere on the box of the headset and i can't find it , i still have the receipt from the shop i bought it and i've asked them if they can help with the problem and they said i need to look for help here. Thanks in advance!