I asked because there was (IIRC) some people having trouble after trying the full TH3 version, which could be activated when opening TH3 SONAR edition.
You should not need a separate serial number for the Boutique FX Suite.
Do you find TH3 under programs to uninstall in Windows? If so, I believe that the full TH3 version have been activated.
You will probably then need to uninstall TH3, reboot, and reinstall the Boutique FX Suite.