Hi there Louise,
Thanks for getting in touch and sorry to hear about this issue. Let’s see what’s going on…
First let me start by saying that there’s nothing you are doing wrong: available filters should display when you activate the plugin alongside The Events Calendar. From the system information you sent, I see the different plugin versions are not matched and that’s most probably the cause of this glitch. All plugins (The Events Calendar and premium add-ons) need to share the major version number (4.4.x at the time). Please try updating all premium add-ons to the latest versions and re-try to see if filters show.
For the updating process, you need to configure the plugins license keys → Automatic updates. As you are using personal licenses in multisite network the update notices won’t show up for subsites (read more on multisite licenses) you might need to update the plugins manually → Manual Updates.
Please let me know if updating the plugins solve this,
Best,
Nico