when I turn my Macbook on it says it cannot connect to icloud because of a problem. What do I do

my Macbook pro is not recognized by my icloud account. Every time I turn on my macbook I get a signal that your device is not connected to icloud because of a problem. I sign in to my Apple account to add my macbook so that it is recognized but it isn't even on the list of devices. What do I do?