[Plugin: WP-dTree 3.3.2] Problem activating wp-tree in version 2.5.1

When I try to activate the plug-in I get this message:

“Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.”

(this is the only plug-in that gives me this message when I try to activate it – so I don’t think it’s the server. None the less I have enquired with my hosting company about this error message.)

https://www.ads-software.com/extend/plugins/wp-dtree-30/