I just reinstalled my operative system and forgot to return my licenses for my Apprintace HD. And now I can't seem to reinstall them. It says that I'm not entitled to any licenses when I try to. How do I resolve this issue?

Try these steps:
http://www.sidefx.com/index.php?option=com_content&task=view&id=1209&Itemid=273#lost [sidefx.com]

If you encounter any problems, please email the output of License Administrator's View > Diagnostic Info to apprentice@sidefx

Problem solved. Thank you!