An internal error has occurred. Daylight simulation has been aborted.

1. Check the DesignBuilder session logs
https://designbuilder.co.uk/helpv7.3/#Diagnostics.htm 

2. Search for the reinsrc.cal in the last session log file:

Daylighting::DoDaylightingCalcs - Command 'cnt.exe 577 | rcalc.exe -e MF:2 -f reinsrc.cal -e Rbin=recno -o "solar source sun 0 0 4 ${Dx} ${Dy} ${Dz} 0.533" >> "C:\Users\LuisS1\AppData\Local\Temp\dkl3athd.imv.Building-1.geom_sun"' failed to run: reinsrc.cal: cannot open

3. You may have installed the standalone Radiance or other software that is using Radiance at some point. Some software overrides the Path and RAYPATH, breaking the Radiance mechanism that DesignBuilder uses.

Solution steps:

1. At Control Panel > System > Advanced system settings > Advanced (tab) > Environment Variables > Under "System variables" and “User variable”, find RAYPATH and delete it.

2. Delete all Daysim and Radiance references on the Path variable at both user and system level.

3. Start a new DB session and try Annual Daylighting.

4 (Optional). Copy reinsrc.cal file from the DesignBuilder installation folder of Radiance ( C:\Program Files (x86)\DesignBuilder\Radiance-5.2\lib) to all other locations where Radiance is installed.