ArcSoft did not leave behind an "offline activation" system like Microsoft. It relied on an online database. When MAGIX shut down the servers, they effectively bricked the activation mechanism for all older titles. No registry hack can revive a dead server.
Do not download from "SerialWarez.com." Go to Archive.org and search for "ArcSoft ShowBiz DVD 2 ISO." These are often abandonware backups. arcsoft showbiz license key work
Unplug the Ethernet cable. ArcSoft can't phone home if it can't reach the server. ArcSoft did not leave behind an "offline activation"