You see this message because Shoppica 2 is not properly installed/configured. This happens usually due one (or more) of the following reasons:
1. You have not installed the Shoppica 2 module. Please, go to admin panel, enter Extensions -> Modules, find 'Shoppica 2 CP' and click 'install'.
2. You have not properly updated your index.php file. It should contain these two lines (near the end):
3. You have not replaced the opencart core files (system/engine/controller.php and catalog/model/setting/extension.php) with these provided with the Shoppica package.
For more information about the theme installation, please read carefully the Shoppica Documentation.
If you think you've made everything according to the installation instructions and this message continues to appear, please contact the support.