why doesn't libeoffice recognise java runtime environment?

Windows 10 64-bit, Java Runtime Environment 8.0_231 installed, but LibreOffice Base won’t recognise the folder as containing a JRE

May be you have a 64-bit LibreOffice version installed but a 32-bit Java version - which won’t work. Please check this Java FAQ

Install a full 64bit JDK instead (or in addition to your existing JRE)?