Host-ID

From the installation guide:

To request a license, know the Host ID of the computer to which you intend to
assign the license. In most cases, the Host ID will be the MAC address of the
active network adapter. For more information on types of licenses and the Host
ID, see Obtaining a License.

Is it possible that the computer you are using has two network (ethernet) interfaces, one for wired (LAN) the other wireless (WiFi)?

I think I would supply the MAC address of the wired interface in your case (having the option to choose), because that one is bound to stay with the computer. The wireless network adapter is more probably interchangeable, and then it's MAC address would be changed as well, with all its consequences.

Success!

Luc

I am confused as you say, that you are offered two different Host-IDs.

As was already said, Host-IDs usually means the MAC-Address of a network interface.

But as I remember, the way this Host-ID is derived has differt from Mathcad 15 and Prime.

In Mathcad 15 a license file bound to ANY network interface present (even a virtual adapter 😉 would be accepted.

In Prime they used a mechanism to determine a so called "primary" network interface and only a license bound to that very interface would be accepted.

So people with more than one NIC (wired, WLAN, Bloototh) ran into troubles, when the deactiveated one of them and it happend to be the one which was determinded as "primary". If this adapter is deactivated, another is detected as "primary" and the license is not valid anymore. It was reported, that for some people PTC support created an additional license file for each possible NIC and they had to point Prime to  the correct one, depending on which one was active or deactivated - what a hassle. I guess using an environment variable this process could be made automatic and transparent.

PTC had provided a utility called cpu_id.exe to list the "primary" MAC-Address -> http://support.ptc.com/WCMS/files/90575/en/cpu_id.exe

Has the behaviour of the single "primary" NIC been changed in Prime 4?

I've experienced much confusment on registering a license, but I found the only way was with a license file. The file is named (something like) Math***license.dat and can be found after mathcad installation in the \windows\program data\mathcad\license folder. You can then copy it to you documents folder for easy access. Choose "license file" for registration/license  method, not a server, and browse/point to the *.dat file when directed. These notes may not be exact, but it's enough to get you there if you have some computer savvy. PTC makes it difficult to register the license. Lousy protocol.