My desktop computer has died, and I need to get the Houdini license on it released so I can put it on another machine. The documentation says that you need to return a license from the machine it's on, but I can't currently do that.

What can I do?

You can email support@sidefx.com. The same thing happened to me and they helped recover the lost license.

Will do, thanks!

localstarlight
Will do, thanks!

If you have internet access on the machine needing the license, once you get the license returned, you could try using Sidefx as your license server which removes the need to checkout the license locally.