I'm curious to find out what's different about your setup, compared with ours. If you are able to use direct access, I'd appreciate it if you could let me know. but our network staff again says the fixes they describe don't apply to our situation. They also said that IPv6 is not compatible with License Manager, though in our case it has been disabled, so our network staff says this shouldn't be an issue. We aren't sure what that means, and why 10.3.1 would still work, while 10.5.1 does not. We contacted tech support, and so far they've told us that the license manager needs to be on the same sub-net as our computers. If we use ArcMap 10.5.1 using our regular ethernet cable or internal wifi we connect to the license manager no problem. Our ArcMap installs of 10.3.1 are able to connect to this same license manager with no problems via Direct Access.
For whatever reason we get a license manager error when trying to use ArcMap 10.5.1 via a Direct Access connection. We are in the middle of upgrading from 10.3.1 to 10.5.1. Has anyone had success using 'Direct Access' and ArcMap 10.5.1?