To resolve ETABS license error #18 (typically appearing as "License Not Recognized! SentinelLM Error #18"), the most effective solution for ETABS 2021 (v19/v20) involves correcting the installation choice or manually linking the license server. Primary Fix: Change License Type During Installation
If you are using a network license, the .lic file must explicitly reference the updated daemon path. etabs license error 18 2021