Make sure to download latest version of Steinberg Library and Steinberg Download Assistant.
Download the file(s)
Make sure the files with Steinberg Library are put where you want them (space consideration). Steinberg remembers where it’s files are!
After opening Symphonic Orchestra you should see that it’s not giving errors regrading it’s files. So, just make sure to open different instruments and see if they load and try!
Hope this helps.