I downloaded Houdini apprentice so I could get familiar with the software…unfortunately every time I try to open it the license server is always opening and the program won't start. I checked my license and all of the options are green and my license does show up. When I uninstall and reinstall the program nothing changes. It just repeatedly asked me to reinstall my license says it was successful and then just cycles through the whole process again. Can someone help me get it to open. I am on the OS X El Capitan if that makes a difference.

If you run it from the shell, it'll usually show some error messages. Go to /Applications/HoudiniXX.YY.ZZ/Utilities and run Houdini Terminal. That will give you a Terminal with the Houdini environment setup for you.

Then type houdinifx -foreground and hit enter. Does it give you any more information in the shell? I've run Houdini 15 under El Capitan on a Macbook Pro (late 2011). What are your system specs?

I tried what you said but it doesn't say anything in the terminal other than the name of my computer. I have a mid-2012 macbook pro. I just updated to 16gb of ram and have a 2.5GHz intel core i5 processor. It does say the houdini environment has been initialized but still doesn't open at all.

Hmmm…. Try running the license server (Administrative Tools folder) or run ‘hkey’ in the Houdini terminal.

Go to File > Change License Server, and see if it says your local computer. If it doesn't, click Local Server, then Accept, and try launching Houdini again.

One place you can look for info are the FAQs (at the top of the web page, go to Support > FAQs, then look at the Apprentice Local Licensing page).

If it still doesn't work, and you can't find anything applicable in the FAQs, you can email support about these sorts of issues. What would be helpful is in the License Administrator, go to View > Diagnostic Information, and include that when contacting support.

Also try to make sure you are an administrator when you first open Houdini.