cannot add account to calendar

Ever since upgrading to Yosemite I have had ongoing and increasing problems with the Calendar app. I have my iOS device set up to sync with my home calendar and it is very important that I get various alerts throughout the day to ensure I keep my schedule. For some reason though, this week the schedule on my computer has ceased being reflected on iCloud or my device.

Yesterday I dug into this a little more only to discover that my iCloud account is no longer connected to my calendar. I am signed into my iCloud account in system preferences etc. But when I go to calendar preferences and try to add an account (all accounts except "On My Mac" have disappeared), I enter my id and password but no account is added. I don't get any sort of error message either but there are no results.

I have looked at troubleshooting options and turned off Calendar in the iCloud preference, waited and then turned it on and reopened Calendar but nothing has changed.

Is there anything that will stop calendar from allowing an account to be linked? I have been using this for years and suddenly it doesn't work. I have to think it has to do with the new configuration of iCloud.

Thanksd