If you have a Creative Cloud "All Apps" subscription and Fireworks is asking for a serial number, it is likely an activation glitch:
If Adobe Fireworks CS6 is prompting you for a serial number, the solution depends on whether you have a standalone license or a Creative Cloud (CC) adobe fireworks cs6 serial number
and is no longer actively supported, Adobe does not issue new serial numbers for it. Where to Find Your Legal Serial Number If you have a Creative Cloud "All Apps"