LiteCommerce:Why...?

..I'm getting "Cannot initialize module: the module license is invalid" error?

The error means that your license (recorded in LiteCommerce admin) does not contain data on the newly installed commercial module. When you purchase an add-on it is registered to your license and the certificate. You should update the license in the admin zone:

1. In "My licenses" section of your X-Cart Account, click on 'Certificate', copy the certificate text (remember to include all the digits), or 'Download certificate'.

2. Go to the store admin area, "Maintenance" menu -> "License" page. In section "Install / Update license", paste the certificate text (or upload the certificate file if you downloaded it from the helpdesk) and click 'Install/update license'.

..I'm getting error that the cart is not installed and I should run install.php?

Most likely the directory "var/" does not have writable permissions (777). Make sure this directory exists. If not, you can create it manually. Then set the 777 access permissions on it. Use "chmod" command to change permissions:

chmod -R 777 var.