My calendars disappeared since I've started using the birthday option

I don't understand why all the events in my calendar disappeared since I started using the birthday option. The "error message" tells me "You can’t add or change events in the Birthdays calendar." but when I check the subscriptions available, "Birthdays" is the onlhy one that is offered to me. Before the issue happened I could choose between work, home, and birthdays. Now, only birthdays is available! Can someone help?