vb6 server will not port to visual basic.net??

i have a server that is called from a vb6 application. the app allows me to add it as a reference. it is a .exe file

when i tried to do the same from a visual basic 2012 in visual studio it gave the message " ... could not be added. please make sure that the file is accessible, and
that it is a valid assembly or com component.

is this an expected feature of the .net visual basic or can i set some switch to allow porting "old servers"

i really think i am out of luck and unfortunately it was written a while ago and the source code is goneeeeeeeeee.

thank you for considering this.