Undefined index: post

It looks like I “forgot” to use isset in a couple places in that file. Usually I develop with debug on so I can catch mistakes like this, but I must have turned it off when I was working on that file. I’ve made a note to fix it on the next release.

The easiest solution to help you right now would be to turn off debug mode, alternatively you could edit the file car-demon/vin-query/car-demon-vin-query-admin.php and add the isset check.

Remove line 94, then
Remove line 46-47 and replace with

elseif( isset( $_GET['post'] ) )
          $post_type = get_post_type($_GET['post']);
     else
          $post_type = 'post';

That should let you install the PlugIn and move on to your next issue.

hope that helps,
-jay