While the free version is sufficient for basic projects, many users eventually upgrade to (v2.x) for advanced professional workflows.
.zip file you downloaded and select Install Add-on.To get the official, working Archipack 2 for Blender 2.8/2.9/3.0+: archipack blender 2.8 free download
This is the version that was available for free before the release of the commercial "Pro" version. It is open-source and free to download. Archipack Blender 2
Advanced roof generation, terrain tools, massive preset libraries, and faster performance. Support: Regular updates and direct developer support. How to Install Archipack in Blender 2.8 (Free Version) Open Blender 2
If the main GitHub link is down, check: