Having this same issue. I've removed stale devices from my family account, all devices are running the latest OS, have been rebooted, controlled for network connectivity issues by trying different networks, have a recovery contact and key set, MFA, etc....and yet cannot enable ADP without receiving a generic error that something went wrong. Trying to enable it on my macbook gives a slightly more descript error saying that there was some "server error". I was put into contact with Apple Support over the phone after initiating a chat session and was basically told that "computers do that sometimes".