When you register the plug-in, you must agree to the license agreement or you cannot register. If you are registering the plug-in every time your solution opens, then the license agreement is going to show every time. You can, however, add an extra parameter to the register function to automatically agree to the license and the window will never show. Add the fourth parameter to the Register function like this:

Plug-in_Register( "FirstName" ; "LastName" ; "RegNumber" ; "I Accept the License Agreement" )

This is only needed for license holders who have Site/Worldwide Licenses that have a startup script which registers the plugin every time the solution starts.

Note, users with a Developer License should not use this parameter, as it will not work correctly. Please see your developer instructions you received when your license was purchased.