Just want to log this in case this comes up with anyone else. I had a rare situation where a working 11.14 license server was upgraded from Windows Server 2012 Standard to Windows Server 2012 R2 Standard. All the installed apps on the server were qualified for the R2 release, including the FlexLM server, according to "Hardware Notes – PTC License Server Last updated: November 22, 2017" from PTC.
After running the R2 upgrade, everything came back except lmadmin. "ptcstatus" gave “System error 10061 ‘WinSock: Connection refused”, indicating the daemon was not running. Sure enough, not only was it not running, but the Windows service "lmadmin" was missing from the Services list.
The remedy was to uninstall and re-install the license server. That was the only way to re-install the service, according to "License Administration Guide FlexNet Publisher Licensing Toolkit 11.10.1", which recommends running lmadmin as an OS service.
Our IT staff had the same problem this past weekend. He did not have the FlexLM software on hand and had to revert his entire upgrade. I Believe he was upgrading from 2008 to 2012R2.
ugh, I hate when that happens. I don't know if the issue is with Microsoft or FlexLM, but it can also happen with certain Windows 10 upgrades. I found this out the hard way when another license server running Windows 10 did one of its "unexpected upgrades". Again, uninstall/reinstall fixed it.
I keep a copy of the latest installer handy. You can find it here.