Hello from Germany,
I successfully upgraded to EN 9.3.1 on a MacBook 12" under Mojave 10.14.6. When opening EN 9.3.1 on my reference library for the first time, it converted it to a library which, unfortunately, was empty. When I try to open my earlier library (which previously used with EN 9.2 contained > 7,000 references) a message appears that EN wants to convert the library into a EN 9.3.1 readable version, but soon after a message appears “This library is currently being used by someone else. Try opening it again later”. The same happens if I try to open any previous versions of the library by doubleclick on the .enl file. Therefore, I cannot use my references libraries with EN 9.3.1 anymore. How to solve the problem?