Help with installing PostFinancial plugin

Hello,

Help with installing PostFinancial plugin.

In My Extension the Plugin is avbailable however I am missing a key componnet.
clicking the install button results in

error: Failed Dependency

Required plugin/package „postfinancecheckout/sdk 3.0.1“ is missing or not installed and activated

What am I doing wrong

Hello, is there anyone who can meet me on Skype to talk me through what I need to do, please

Skype: britepencil