I have a MacMini that was having issues. It had OS X 10.9 and OS X Server 2 I believe. (With all of our users and settings etc)
I took the Time Machine Backup from that and transferred that data to a brand new Mac Mini. This Mac Mini had 10.11 installed on it already. The data transferred fine - but the OS X Server icon is greyed out. That's fine, I go to the App Store to upgrade the application and it doesn't let me because the OS (10.11) is too new. That's fine, I go try to buy MacOS Server 5 which is the newest version. It doesn't let me because it requires Sierra to install. Fine, I go download and install Sierra... but on the screen where I select which disk to install it to, it doesn't let me and says "macOS Sierra supports macOS Server version 5.2. To upgrade server data, you will first need to install OS X 10.10 or 10.11 and OS X Server version 4 or 5.
SO. I can't upgrade to macOS Server 5 because I don't have Sierra. I can't update to Sierra because I don't have macOS Server 4 or 5.
I can't access macOS Server 4 in the app store and any direct links I found to it just link back to macOS Server 5...
What can I do? Am I just going to have to rebuild all my users and settings in macOS Server?