Buddypress Group Calendar Error

Upon activation attempt I get this message. "The plugin does not have a valid header."

Is there a fix for this?

Update:

I'm now realizing I'm having trouble installing any WPMUDEV plugin... I get various errors including "fatal error" and the message "this plugin is only available for multisite" that pops up no matter where I go in the dashboard. (I had to log onto cpanel and manually delete.)

What could be causing this?

Update 2: My less plugin-heavy site http://www.midwestwisters.com has no issues activating Group Calendar Plugin... I imagine that this is a plugin issue. I'll do some diagnostics....