Razer Cortex is a Windows application for game optimization and management. An "offline installer" is a full installer package you download once and run without needing an active internet connection during installation.
Solution: You have downloaded the 64-bit version but are trying to install on a 32-bit version of Windows. Razer Cortex requires 64-bit Windows 10 or newer. Check your system type in Settings > System > About. razer cortex offline installer
Before running any downloaded file: