Hi Lewis,
Thank you for reaching out here at the Microsoft Community Forum.
We see that you have concerns about the subscribed calendars that are not updating. We understand how important it is to get this addressed. Allow us to check on this and we’ll assist you in the best way we can.
Based on this article: Import or subscribe to a calendar in Outlook.com, under the sections: Subscribe to a calendar and The difference between importing and subscribing to a calendar wherein it states that the update can take more than 24 hours, though the expected updates should happen at least every 3 hours. However, this is not the case on your end since it has already reached a week and you were not able to see any updates.
We acknowledge that it only updates when you remove and subscribe again to the calendar. To identify if this is somehow related to the subscribed calendar itself or may have something to do with the account instead, may we confirm if this issue just happens recently, and it supposed to update right away whenever there are changes made to the calendar you’ve subscribed to?
For further isolation, have you already tried checking using other web browsers aside from the one you’re using and check from there if the issue persists? If you haven’t done it yet, you may try to do so and see if there any improvements.
The question and suggested step can help us narrow down the cause of this issue, so we can provide further recommendations in our next reply. We’d love to hear from you soon.