License Error 18 2021 - Etabs

The 2021 release of ETABS coincided with major Windows 10 updates (20H2, 21H1) that hardened security around system services and network tunneling. Here are the three main culprits specific to that vintage:

Even if lmgrd is new, the vendor daemon ( CSiBridgeDaemon.exe or similar) might be stale. ETABS 2021 looks for a specific feature signature. etabs license error 18 2021