Hi. Thanks for your question.
You need to install the core/free The Events Calendar plugin, which is sounds like you have. The add-on links viewable from wp-admin > Events > Event Add-ons are not “smart” links. They don’t know that your account already has access or even if some or all of the add-on plugins are already installed and activated.
You need to download and install the .zip files available at My Account > Downloads.
You install the files by going to wp-admin > Plugins > Add New > Upload Plugin, and you upload the .zip file you downloaded. Then, once installed, you click to Activate it.
I hope this clears things up.