Q: Connection problems icloud

Hi - I changed my Apple ID about a year ago.

For the last few days, I've been getting messages saying my Mac cannot connect with icloud and gives the old and out of date, email address that I stopped using a year ago. I'ved checked my details with the Apple ID system. Everything is up-to-date. Have double-checked the system does not recognise the old email address or the password connected with it.  How do I stop the message saying there is a connection problem?  Many thanks