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Configure the user profile on the Object Settings when the tab is not visible.
Go to Setup > Profile > Standard Platform User / Standard Platform One App User / Standard Platform Choose the Profile for the Internal log-in User > Object Settings > My Calendar > Default On > Save.
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Note: You need to configure the Profile of the User that you want to give access to the My Calendar tab component.
In the Standard Platform Internal log-in User profile, go to the Apex Class Access and the following Apex Classes
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