Trying running SX3 with a Cubase Pro 10 license

Hi. I need to open old VST/24 files and I remember I did this task by using Cubase SX3 to import VST/24 arranges and save as .cpr. Then they were able to be opened in newer Cubase or Nuendo versions.
I own a Cubase Pro 10 license and several Nuendo 8 and 10 licenses and I keep several Mac G4 and G3 machines with SX3 installed. Before update to Cubase Pro 10 I was able to run the Cubase SX3 versions with my dongle but now no license is found. I’ve tried to install the last e-license version of the OS running in old Macs (10.4 and 10.5) but when e-license updates database a message of all is updated appears. Then you try to run again SX3 and license error… and so on.
What’s the way to run Cubase SX3 with a Cubase Pro 10 license?