The error message you provided is indicating that there is an assertion failure in the Embree.cpp file of the UnrealLightmass.exe program. This error is related to the Embree library, which is used by Unreal Engine’s Lightmass system to perform ray tracing calculations.
The error message states that the Embree device returned an error, specifically RTC_NO_ERROR, indicating that there is some issue with the Embree library that is preventing it from functioning properly. This error can be caused by a variety of factors such as outdated graphics drivers, a problem with the Embree library installation or conflict with other software running on your computer.
Some solutions that you can try to resolve this issue include:
Updating your graphics drivers to the latest version.
Make sure your system meets the minimum requirements of Unreal Engine 5.
Reinstall Unreal Engine 5 to ensure that all necessary files are in place.