Q: Unable to add an OS X Server Account to iOS device or Mac

I have made some minor progress on this.  In asking around - and doing some experimentation on my own - I rebuilt the Mac Mini and Server with a clean install of El Capitan 10.11.3 and Server 5.0.15.  Surprisingly the problem still happens.  I run my home server as a non-registered as well as non-delegated subdomain of my registered domain - thus I had my host name as server.home.example.com  (with example.com substituted for my actual registered domain).  In this configuration all DNS functionality and services (except for add os x server account) were working perfectly.  This is private DNS - not public facing - port 53 blocked at the router.  In DNS - my primary zone was home.example.com with server.home.example.com as the name server.  I changed the DNS config to be a primary zone of example.com with server.example.com as host name and name server.  Surprisingly - the Add OS X Server account functionality works.  The downside of this is that I cannot access my external domain from inside my network - and that was the reason for the subdomain setup in the first place.  I tried a number of different DNS and subdomain configurations - and basically when the host name contains more than two dots (.) (e.g. server.home.example.com) the Add OS X Server account reports invalid user or password - as if it's not reading the correct open directory.  So - I can use {anyname}.example.com as the host - and everything works.  I wonder if this is actually a bug?  I have somebody looking at my DNS zone files to see if there is anything unusual.  I have read most of the DNS and Bind book and I can't see anything wrong - configuration wise - but I am not a networking professional and I'm doing this more as a learning experience.  Just curious to know if the others that have indicated that "they have this question too" are also using a "subdomain" DNS setup?

~Scott

The Add OS X Server account functionality currently has a limitation of 24 characters on the length of fqdn (fully qualified domain name) of the hostname whether it is referencing nth-level subdomains or not.  Example: If your hostname is testingserver.example.com  you will get the error - because the fqdn is longer than 24 characters.  If your hostname is server.sub.x.example.com - everything will work fine - because the total length of the fqdn is 24 characters or less. This limitation applies to .private host names as well.  If you need to use OS X Server accounts feature - the workaround - at least for the time being - is to ensure that the fqdn of your hostname is 24 characters or less.  This may be difficult if you don't have any ability to shorten your domain or subdomain name.  This has been reported to Apple.

~Scott

The workaround above is the result of my testing and experimentation and appears to be consistent behavior in my environment.  It does not represent any acknowledgement or confirmation of a problem - nor any guarantee of a fix from Apple.  I am posting my findings in an effort to help those that are experiencing this issue.

The update to Server 5.1 appears to correct this issue.