CATIA V5 R21 uses DSLS v6.4 or earlier. Modern Windows 11 blocks the server’s self-signed certificates.
He realized his mistake. He had ignored the "Updated" part of the equation. Windows 11 was a moving target. Microsoft had recently pushed a major security update (KB50xxxxx), tightening the screws on legacy software permissions. The old R21 installer was trying to write to system directories that Windows 11 now treated like Fort Knox. install+catia+v5+r21+on+windows+11+updated
He wasn't just fighting an old program; he was fighting a modern operating system designed to protect itself from exactly the kind of outdated code he was trying to run. CATIA V5 R21 uses DSLS v6
Find CNEXT.exe again:
After installation, the server service (DS Licensing Service) will fail to start. Open Services.msc, find “DS Licensing Service”, and: find “DS Licensing Service”
Although CATIA V5 R21 officially requires Windows 7 or 8, a Windows 11 installation demands:
R21’s license management tools (DS License Server) need .NET 3.5.