Starting in Data ONTAP 8.2 all license keys are 28 characters in length. With an upgrade existing licenses should be unaffected, however if you reapply a license then you must use one of the new ones. The new 28 character licenses for the systems can be found on the MySupport site under My Support > Software Licenses.
It may also be down to supported versions of OnCommand.
For ONTAP 8.2.5 only the following OnCommand versions are supported: