Hello Guys
I'm quit new here, but i was suffering the same problem and went crazy try to find soultions. I searched a lot all blogs and apple community replies but no way. With ry and error i come to that solution and it works now.
1- Go to you mail app/Perefernces/Uncheck the box to disable the iCloud from your mail
2- Go to iCloud pereference pane ( you will find your mail unchecked already )
3- Check your Notes ( you will be asked to merge notes with your iCloud account ) / accept
4- With you notes already checked, check your mail again
5- go to your mail app again, to make sure you recieved a mail from iCloud to let you know that your account is activated.
It is all good and work for me
Hope that will help you too
Thank you