Error "can only init the Organizer Module once" / "Submodel does not exist: catalog"

Dear Community, 

my installed version of Lightroom CC via CreativeCloud won't open correctly - the following error messages show up, I have no possibility to access the application. I have reinstalled via CCCleanerTool already, no solution... As I am also having issues with synching Lightroom Classic to CC (see my other active post)... Regards