Hello @listlove,
Sorry for the trouble here with installing the update to Events Calendar PRO!
I looked up your account and see that the plugin’s license is currently registered to: www.livelovelovelife.be
When I visit your site, though it looks like the calendar is installed on: http://www.livelovelovelife.org
Are you trying to install the PRO update to one site and not the other? You can move your license key from one site to the other by following the instructions outlined in this article. Please note that the plugin can be installed on as many sites as you want, but the license key can only be registered to a single site at the Personal license level. Either way, the plugin will work with or without the license key.
Thanks!
Geoff