Support for the Platform Manager was added into ispVM System starting at version 17.9. Earlier versions will not recognize Platform Manager correctly.
Currently, Lattice recommends using Lattice Diamond Programmer tool for programming all the Lattice devices.
It provides support for Platform Manager devices too.
Download the software from the below path,
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.