On a multiuser system Cubase 13/Halion Sonic 7.1 didn’t show any Halion instruments when being used with a account (student) not being the user who installed Cubase (admin).
Reason seems to be that Steinberg Download Assistant seems to download the files (i.e. Halion Sonic Selection content) into the Downloads folder of the installation account (admin user) and then moves the VST Sound content with explicitly set permissions to the public ProgramData folder (Windows has specific permissions on the Downloads folder (only accessible to the current user (installation user) and administrators)).
Being not able to access some VST Sounds in the ProgramData folders seems to break the Media bay server so that even the still accessible instruments were not shown.
Workaround was to force the permissions on
C:\ProgramData\Steinberg\Content\VST Sound
C:\ProgramData\Steinberg\Content\Halion\VST Sound
(maybe other VST Sound folders)
and subfolders to be inherited by the parent folders (which include user read access).
The real solution would be an update to the Download assistant to ensure the correct permissions for files in the ProgramData content folders.
Already reported this with the above workaround to German Steinberg Support one month ago, but received an automated response with excuses for the delay and the information that I should create a new ticket if the issue persists. So I fear the issue has not yet reached the people being able to fix this two issues (wrong permissions set on VST Sound content by Steinberg Download Assistant and media bay server/Halion not handling insufficient permissions gracefully) permanently.