DP8 is set by default to open in 64 bit on 64 bit systems. If a plugin is only available as a 32 bit plugin it will not show up in DP8 running in 64 bit.
To switch DP8 to 32 bit, go to Macintosh HD/Applications. Single click the Digital Performer icon to select it, and then choose Get Info form the File menu. That will open up an Info window. Check the box labelled “Open in 32 bit mode.” Re-open Digital Performer and it will open in 32 bit mode.
Plugins that are only available as 64 bit plugins won’t show up in DP8 under 32 bit mode.
Another reason that a plugin may not show up in DP8 is if the plugin is only available as VST or only as an Audio Unit plugin and the Primary External Plugin format is set to the opposite format. The plugin would not have been enabled by default.
Go to the Digital Performer menu>Preferences, then in the General category choose Audio Plugins. If the plugin shows up in the list but is disabled, enable it by checking the box next to the plugin.