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. This is a common situation, because Java home page (only offers 32-bit JRE by default, regardless which is current operating system architecture. 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. 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.
