Hi all:
I had the same issue for over a year and finally had a breakthrough yesterday after talking to a super Apple Support Senior Advisor (Mac T1) for over two hours. It turns out, my old "legacy" Apple ID had an issue when everything was converted from me.com accounts to iCloud.com accounts. The issue as to why the initial Apple ID was "damaged" is still up for review, however, after creating a new Apple ID and then systematically signing out from all devices the old one was associated with the problem was fixed right there.
We found that things like Calendar, Notes, Mail, and Find My Friends were not working properly and all of them had my sign-in for my original Apple ID. Here is a simplified overview of what we did:
We created a new Apple ID as a fresh account > Signed out of any and all accounts that had the old Apple ID > Signed in to each account individually with the new Apple ID > Done.
Items in your iCloud Notes, Contacts, Calendar, photos in iCloud come off of your devices, HOWEVER, stay on iCloud.com under that legacy Apple ID, so you can still retrieve them and get them transferred to the new Apple ID (I double-checked this and found everything to be safe). Your Find My Friends app has the new Apple ID and you only need to re-invite your friends and family and have them reciprocate and all will work (seeing where they are, notifications of them coming/going, etc.).
To sum it up, the old "legacy" Apple ID may be corrupted in some way when the new transition to iCloud came about. Device hardware, the app itself, and notifications in Settings should have nothing to do with the "Server Error" message.
Good luck!
FAMFOBOS
