If LightBurn is open the installer won’t overwrite it.
From a fresh restart, before you start LightBurn, click on the .exe file that your browser downloaded.
Post some pics of the picture you’re trying to burn. Sometimes right-clicking the file outside LightBurn and selecting ‘Details’ can be informative. Try to screen cap the ‘preview window’ in LightBurn and we’ll try to figure out what’s going on.