If you are running need to run Maya 2011 and you have a Subscription Maya Creation Suite 2013 license which allows you to run Maya 2013 - 2010, you will need to re-generate a license today on Register Once.
For details on the process of registration, please check out this post:
If you generated license before July 18, 2012, you will notice the following if you use the license parser on your license file, Maya 2011 is going to use try to use the code 85687MYECSP_2011_0F to launch.
Also, if you check the Casscade Order for 2011 products, Maya 2011 is looking for 85620MYECS_2011_0F and not 85687MYECSP_2011_0F.
Autodesk Maya 2011 Cascading Sequence:
Autodesk Maya 2011
Autodesk Education Suite for Entertainment Creation 2011
Autodesk Animation Academy 2011
Autodesk Maya Entertainment Creation Suite 2011
When you check out the Flex Codes used in for Maya 2011, it uses the following:
Autodesk Maya 2011 | 85537MAYA_2011_0F
Autodesk Maya ESC 2011 | 85620MYECS_2011_0F
If you use the license parser on an older Maya Entertainment Creation Suite 2013 license, you will notice that Maya 2011 license code is 85687MYECSP_2011_0F.
This is a sample Maya 2012 Creation Suite license and it contains the correct Flex Code 85620MYECS_2011_0F to run Maya 2011.
This is the corrected license file for Maya Creation Suite 2013.
Thanks to Lap Ho, Alek Valle and the development team for assisting in resolving this licensing issue.