My mac isn't showing all of my calendars?

My MacBook has stopped showing all of my iCloud calendars in the calendar app. The calendars view fine on all of my other devices including my iPhone and iPad but they're missing on my Mac.

The strange thing is that on iCloud.com the calendar timings are all out of sync, so where events on my iPhone say 9am - 5pm (which is the correct time) on iCloud.com they're showing as 9pm - 5am? huh? Could this be why my Mac is confused?

Also some of my calendars are collaborative with other iCloud users so that we can add events into our calendars. When events are added they come up as notifications on my Mac but then can't be seen in the calendar app on my mac!

Any ideas?