If you run into any issues with DLPAR not working correctly try the steps below to restart the RMC service. We have seen this procedure work in the past to rectify the problem.
On the HMC command line, first check the DCaps value of the LPAR. If the value is DCaps "<0x0>" there is an issue with the RMC connection on that LPAR.
# lspartition -dlpar
<#1> Partition:<6*9117-MMA*xxxxxx, , 10.x.x.x>