The following Multisite screen will be seen if you have the Multisite Network setup activated. My Calendar > Settings > Multisite.

Multisite installations can be fussy, and there are a few things to know about configuration.

First, if you want subsites to be able to post to their local calendars, don’t use Network Activation to activate the plugin globally. Global activation works, but only supports posting to the central calendar. This is because the individual site database installation only runs when the plugin is activated on that site.

Screenshot showing the panel of multisite options described in the article.
My Calendar > Settings > Multisite

Multisite configuration – input

Site owners may only post to their local calendar.
Site owners have access to post only to their own sub site calendar. All events created in the sub site are listed on their local events calendar.

Site owners may only post to the central calendar.
Site owners can only post to the primary site calendar. All events created in the sub site are sent to the central calendar.

Site owners may manage either calendar.
Site owners can manage their own sub site and the primary (sub) site calendars. They’ll be able to select which calendar a given event is posted to at event creation.

Multisite configuration – output

Sub-site calendars show events from their local calendar.
Show events from only the sub site calendar.

Sub-site calendars show events from the central calendar.
Show events from the primary sub site calendar.

Multisite configuration – shortcode

The main calendar shortcode supports an argument to display events from any other site on the network.

[my_calendar site="2"]

The site parameter accepts the ID of any site on the network, and will pull events from that site.