LibreOffice can only use JRE with matching architecture: i.e., 64-bit LibreOffice can only use 64-bit JRE, and 32-bit LibreOffice can only use 32-bit JRE. When you have installed a 64-bit LibreOffice, and 32-bit JRE, LibreOffice would not be able to find and use the JRE, no matter how hard you would try it. This is a common situation, because Java home page (www.java.com) only offers 32-bit JRE by default, regardless which is current operating system architecture. In this case, LibreOffice (of reasonably fresh version) would try to be helpful in its error message, telling you that it needs specific architecture (e.g., 64-bit) of JRE. To find other available downloads, including 64-bit JRE, you need to ignore the Big Red "Agree and Start Free Download" button, and find a small See all Java downloads link below.