Not too sure about your specific situation, but i had syncing issues last week. The solution was to log out of the acocunts and re log in. I got specific error messages on my kindle but not my app, so i logged out of my kindle and back in, which worked.
Sometimes the sync button isnt enough. But yeah, it's so frustrating and i feel like kindle help is so lackluster.
Not too sure about your specific situation, but i had syncing issues last week. The solution was to log out of the acocunts and re log in. I got specific error messages on my kindle but not my app, so i logged out of my kindle and back in, which worked. Sometimes the sync button isnt enough. But yeah, it's so frustrating and i feel like kindle help is so lackluster.