Hi. I have been running an MCU 5310 in my lab since PCA first appeared on the market (release 9.0 back in 2012). It is currently running 4.4(3.49) and managed by PCA 11.5 SP1 as well as 11.6 ES4. Please make sure that the user you created for PCA to access the MCU is set to administrator privilege level on the MCU. If that is already the case, then I suggest you open a TAC case. /Phil