apple id

I began with an apple id years ago. Within the last 6 months, I have changed my email address associated with the apple id. Some functions on desktop are not performing. A window continually comes saying "This Mac can't connect to icloud because of a problem with my email address. Open icloud preferences to fix this problem." It will not allow me to continue.

1. How do I straighten this out?

2. How do I get all other devices on board?