If you cancelled the light build and didn’t save on exit it is likely using the previous build. If you’re using Swarm with the Binary release my swarm agent guide has some useful info for cleaning the cache and validating, and clearing the derived data cache.
If you’re using a source build, it’s not uncommon for some to have issues with Swarm Agent because Lightmass wasn’t built properly when compiling. This often leads to issues with “Swarm Failed to kickoff” errors, though. In that instance just rebuilding UnrealLightmass should work.
Beyond that, it’s a little hard to say offhand what exactly caused what you’re seeing if it doesn’t line up with this.