Should the PARTsolutions menu not be visible, please check whether PsolAdeskinvAddin Class is activated under Tools -> Add-Ins.
Example: Add-In Manager 2010
Example: Add-In Manager 2017
Make sure that "Load On Startup" is activated.
As of Inventor 2017, when using a Sales Offline CD the following adjustment has to be done in addition:
Open %appdata%\Autodesk\Inventor 2017\Addins\cadenas.PartSolutions.Inventor.addin.
%appdata%\Autodesk\Inventor 2017\Addins\cadenas.PartSolutions.Inventor.addin
There, under <Assembly> enter the full path to Inventor dll.
Example:
...\sales_offlinecd-...\iface\inventor\2017_64\ifadeskinv2017_64.dll