Windows 10: Windows 10 Calendar app does not sync with Office 365 Outlook calendar

How do I sync the Calendar app calendar with my Office 365 Outlook? I have checked all sync settings and everything should work, but it doesn't. I'm running Windows 10 1809 on my computer. When I go to Calendar in Outlook, the rotating dot circle keeps running and doesn't find anything other than my Outlook calendar.

:)

 

Windows 10 Calendar App / OUTLOOK.COM


Ok I'll try it this way and post my steps. Please feel free to let me know if I#m missing something.
I just added a calendar:




As you can see by today's date it took immediately in the online version:




Now I'm just waiting for it to sync to my app:




By the way it was synced right off to Outlook 2016 in Office 365:

 

Online Outlook Calendar not syncing with Windows Calendar App


Hello everybody,
my online outlook calendar does not sync with my Windows Calendar app. I am talking about the online calendar which can be accessed after sign-in here: Prihláste sa do svojho konta Microsoft which for me used to always take all the information from my desktop calendar app, and vice-versa, when I entered an event online, it also appeared in my desktop app. This was useful for syncing with my phone and generally accessing my calendar when not having my laptop on me. This is now impossible for me to do.

Now they don't sync and it's quite annoying, I am getting desperate and thinking of using some other app (if you have tips, tell me. I went through this: Resolve sync issues in Mail and Calendar apps in Windows 10 - Office Support it did not solve the problem. I have updates on (I apply them manually). I have Windows 10 all up to date. and all settings allow calendar to be synced. I checked if I am signed in to the same account, I only have one account in the app and the same one online.

Thank you in advance for any help.

Also, I am adding a picture if it helps, on the left is my calendar, when I access it online, on the right is my Windows App. You can clearly see that there is a lot more on the right. I just want the events to appear in the online calendar as well, as they did before...

 

Windows 10 Calendar App / OUTLOOK.COM


@Pocks1954, this morning when I got up and fired up my main machine, it finally (also)synced the new calendar I created online at Outlook.com:




Now I will delete the calendar there, and see how long it takes to disappear from my UWP Calendar apps on all my machines, and from Office 2016:

I went here to delete the newly made one: Sign in to your Microsoft account

It disappeared from my Office Outlook 2016 calendar immediately,

It is also gone from my Insider VM calendar app:




Gone from my laptop too:




As I was getting the various screenshots from my other PC & VM, the calendar that took a day to sync to my desktop, also disappeared:



So as this is the second time I tested this, I suspect the problem(if you actually deleted the online version of the calendar)has either something to do with your machine syncing to OneDrive, or sync & location settings in the Settings app, or the sync settings in the Calendar and/or Mail app itself(check these settings):