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Hi.
Welcome to Microsoft Community.
In order to sync the calendar across devices, I would suggest you to configure your email in Outlook as Exchange active sync.
Let us refer to the following link and check if it helps.
https://blogs.office.com/2012/11/15/put-the-power-of-outlook-2013-behind-your-outlook-com-email/
If you need further assistance, get back to us with the required information and we will be glad to assist you.
Thank you.