Check the version of ispVM you are using from the title bar or the menu item Help->About.
Only ispVM versions 19.7 (or later) will correctly identify the Platform Manager.
Currently Lattice recommends using Lattice Diamond Programmer tool for programming all the lattice devices.
You can download the same as below:-
Go to www.latticesemi.com
and log in to your lattice web account.
Go to Products > Design Software & IP> Programmer and Deployment
Tool
Below is the link for the same,
http://www.latticesemi.com/Products/DesignSoftwareAndIP/ProgrammingAndConfigurationSw/Programmer.aspx
Under 'Software Downloads & Documentation' section, under DOWNLOADS
tab, select Downloadable Software and download the Standalone Programmer as per
your system requirements.