I had this same problem, I have found a fix. When you link drop box to the technic platform make sure ou replace www. with dl.
Like this: https://dl.dropbox.com/s/fg7pcbttorb9m6a/Teh Grover Modpack.rar
Not like this: https://www.dropbox.com/s/fg7pcbttorb9m6a/Teh Grover Modpack.rar