When you copied the add-on files to your server are you ABSOLUTELY SURE that you found EVERY instance of YOUR_TEMPLATE and change it appropriately to the actual template name?

I say this for 2 reasons: 1) This appears to be the reason behind many add-ons not working upon installation and 2) Because there are SEVERAL locations within the subscribe add-on files structure which require you to change the default template folder name (YOUR_TEMPLATE) to your actual template name. One in particular that I just looked at is buried in "includes/templates." This happens to be where the sidebox contents are location. Without this path being correct, the admin console wouldn't know you added a sidebox.

When you finished installation and pulled up the layout boxes controller, were you greeted with a message at the top that said something like "new sideboxes found?" If not, you definitely did not copy over the correct file structure.

As a newb myself, I can confidently stress that making sure the file and folder structure is correct is the #1 priority when installing add-ons; I have about 10 under my belt to date, all of which work flawlessly. #2 by the way is simply following the instructions to a T.

HTH.

Jason