Syncing calendar, Reminders and notes

Had successfully set up syncing between my iMac, IPad and my wife's iMac, iPad and macbook air. For some unknown reason it stopped syncing after about 4-5 months. Not able to figure it out and resending invitations don't work, so, looking for a resincing work around.

Any help in this area would be greatflully received as am a bit off knowledge with this one.

We now gave the above plus iPhones as of a week ago. So desperate, as we are running our small business on them.

Best regards