Mac Server: Unable to update Server

After updating the OS on a Mac Mini to 10.12.6 and downloading Server.app 5.3.1 we encountered an error:

It turns out that not all OS/Server.app versions allow direct updates; in some cases you must do a data migration.  Apple posts an upgrade matrix here.

The quick fix, if you don't mind configuring the server again, is to simply trash the Server.app from Applications and remove the /Library/Server folder.  Once this has been done, you can re-install Server.app and it will launch the configuration manager.

If you get the "unable to update server" error and you need to keep your settings then you are in for a bumpy ride.  You have no choice but to do a data migration between two devices.  The procedure is explained in the same link as above and entails building a new system, target booting, doing a data migration and then installing Server.app.  Honestly, Apple couldn't have made it any harder if they tried.

Mountain Lion Server: An SSL error has occurred and a secure connection to the server cannot be made

After a recent Server.app update I was unable to log into a Mountain Lion server. 

I deleted Server.app from the Applications folder and downloaded it again from the App Store.  When I launched Server.app after the download it asked for the administrator credentials and then displayed the error "An SSL error has occurred and a secure connection to the server cannot be made."

My solution was to open Keychain Access, click on "System" (under Keychains) and then "Keys" (under Categories) and delete all the keys referencing my server name.  This includes both public and private keys so OS X will prompt if you really, really, want to do it.

I also removed the certificates for the server under System/My Certificates as well as "com.apple.servermgrd".

I crossed my fingers and restarted the server.  I logged in as local admin, launched Server.app and was able to configure it normally.  After the server was up and running I looked in Keychain Access and all the certificates had been re-populated.

Apple's KB on the problem wins the prize for the least helpful tech note ever.  You can see for yourself here:  http://support.apple.com/kb/TS4493.  All they suggest is upgrading to Server 2.2.1.  Guess what I was running when I encountered the error?  2.2.1.  What upgrade locked me out of my server?  2.2.1.  Thanks guys!

Apple Server Admin Not Starting

Problem: OS X Server Admin will either not launch or after it has launched it will not allow connections.

Fix from Apple:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.servermgrd.plist

cd /var/severmgrd

Note: verify that you are in the right path, because the next command will delete everything in the current folder.

rm -rf *

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.servermgrd.plist

Server Manager should now launch and allow logins.