You must locate the old version of SonEQ and delete it, then install SonEQ free 1.2 from the installer
Locate the old file on Mac Osx
AudioUnit: Open "Finder" press Command + Shift + G and paste /Library/Audio/Plug-ins/Components/ then remove the file SonEQ.component.
VST: Open "Finder" press Command + Shift + G and paste /Library/Audio/Plug-ins/VST/ then remove the file SonEQ.vst.
Locate the old file on Windows
On 32 bits Windows systems the older SonEQ.dll file can be founded at "C:\Program Files\Steinberg\VstPlugins"
On 64 bits Windows systems the older SonEQ.dll file can be founded at "C:\Program Files (x86)\Steinberg\VSTPlugins"
If you are unable to locate the solution you are looking for, and you have a Sonimus account, you can still get help by creating a client support ticket.
If you don't have a Sonimus account create a guest support ticket.