This problem is similar to the unresolved issue found here: https://docs.microsoft.com/en-us/answers/questions/417261/error-on-adding-subscription-on-events-usi...
I have a client that uses my web application that uses several different calendars for scheduling. All of the calendars function as expected except for one. For one of the calendars, I can read their calendar events, but I cannot post a subscription to the calendar event causing syncing issues when new calendar events are created, updated, deleted and a manual sync is not performed. This is causing a lot of frustration for my client because we have exhausted any issues that could be responsible for this on our end over the past two months and it very much seems to be an outlook issue very similar to the one in the URL above. I would appreciate if someone could view that calendar and see if there is some kind of problem with the account, otherwise if there is an existing workaround or solution I would appreciate it.
