Cardav authentication message for Yahoo contacts on iPhone
A Cardav authentication message pops up on the iPhone intermittently saying that a password is required. The issue is that my uncle (the user) is wedded to using Yahoo for all his reminders and calendar entries so Yahoo has to stay on his phone. He has everything synced through iCloud, but because he is using the web-based Yahoo calendar and reminders, the only way to get those onto his phone is to have a Yahoo account logged in on his phone for those two features.
Yes, the ideal solution is to stop using Yahoo and move everything over to Apple, but at 84, he's not going to change. Can anyone help save my sanity and suggest a solution for this?
iPhone 6 Plus, iOS 11