Since you are dealing with a 2021 version (which is no longer the latest), prevention is key:
She had one option: the old 2019 laptop in the storage closet. It ran a borrowed, standalone license—a relic from a previous merger. She dug it out, blew off the dust, and booted it up. ETABS v18 was installed, but the license file was for 2020. It would never run a 2021 model. etabs license error 18 2021
: Ensure your computer's date and time are accurate. A discrepancy between the system clock and the license's valid period will cause an immediate failure. Check License Path and Settings : Since you are dealing with a 2021 version