I tried to upgrade my License Server and my Desktop clients to ArcGIS 10.6 from 10.5.1 last week, but I have been getting some strange results. On client PCs with desktop <= 10.5.1, Administrator on client shows all my licenses are available and borrowing is enabled. Once I upgrade the client to Desktop 10.6, Administrator shows no available licenses, borrowing is not enabled, even though Desktop 10.6 and Pro 2.1 on the same client PC start and run normally.
In the attached image, PAUL-WIN10 is a client PC running Desktop 10.6, NSMAP is the 10.6 license server. https://www.dropbox.com/s/p4lcjqyt0h5svx4/ArcLicenseServer.jpg?dl=0
At a different office that I manage, different LAN, this upgrade went without a hitch.
Is the License Manager Name pointing correctly in the client machine (ArcGIS Administrator)? Maybe you should try defining a correct port number as well (27000-27009). e.g. 27001@NSMAP.
Also ensure the above ports are allowed through firewall.
Yes. Those are all the obvious answers. I tried pointing at the license server by name and IP number. Ports are open, I went through this several years ago with the Netgear router I still have. https://community.esri.com/thread/174271 I had normal behavior with Desktop 10.5.1. and License Server 10.5.1. I rolled license server back to 10.5.1 on Monday just so it would working normally for my team until I had a chance to work on it again.
ESRI tech support had me install a license server patch, https://support.esri.com/en/Products/Desktop/arcgis-desktop/arcmap/10-6#downloads?id=7521 but it didn't change anything.
Service.txt looks like:
SERVER this_host ANY 27000
VENDOR ARCGIS PORT=1234
FEATURE ACT ARCGIS 1 permanent 1 vendor_info=7KNJDRHFHBK4CFDMJ214 SIGN="052E ABFC 32DD \
2473 DEFD E276 4BF3 E0DB 87EB 2203 5A30 C014 19A1 C35E 2154 \
08B1 9460 A2B9 6701 DC4D CAF2 E2FE 1347 0E36 90FA 4F3B E864 \
BEC8 D3A2 A615"
Both those ports appear in the Inbound rules on the license server's firewall: https://www.dropbox.com/s/7pciewhuwos1yoq/Screenshot%202018-03-08%2014.01.13.png?dl=0
This problem mystified ESRI Customer Care and myself for several days. Finally, ESRI suggested a download of a patch from https://support.esri.com/en/Products/Desktop/arcgis-desktop/arcmap/10-6#downloads?id=7521 thinking that software on my Server and on my clients was from slightly different builds. At first, it didn't seem to help, but then next day, after restarts of the client PCs, the problem was fixed.
I don't know how I would have gotten a mismatch of builds since I downloaded the License Administer and Desktop 10.6 from the same My ESRI>My Organizations> page. And on Monday, I took my USB drive with what I thought were the same downloads to another office and the upgrades went without a problem. And the license server was working well with Desktop versions <= 10.5.1.