Strike through on calendar alerts with the message Alerts for this calendar are disabled. To allow this alert to fire, enable 'Event Alerts' in the calendar settings for 'Calendar.

Out of no where my calendar alerts is no longer working and has a strike through it. I have tried all the suggested fixes on previous thread where others have the same issues and these do not solve it. My notifications and sounds are on. I rely on these a lot. This is the message I get - “Alerts for this calendar are disabled. To allow this alert to fire, enable 'Event Alerts' in the calendar settings for 'Calendar.”

I have done this and still no joy.