I don't know what I can do more.
You have video and also a PDF that explain thing step by step.
You must use your account where you buy the product.
Otherwise, your product list is empty and you can not get its latest version.
FAQ =
www.jms2win.com/en/faq/faq-joomla-multi-sites#cat-122
Video =
tutorial.jms2win.com/joomla/multisite-12...stversion/index.html
PDF =
www.jms2win.com/en/documentation/doc_dow...t-the-latest-version
When you have got the ZIP with the latest version, go in your master website and use the Joomla extension manager to install the package over the current one.