Compellent SC shutdown hangs

Hi,

I have an 2 * SC4020 + SC200 expansion chassis configuration, running an SCOS 7.1 version.

When trying to shutdown the system via the web interface to the data collector, the interface hung shutting the first storage center. It appaers that the actual sc4020 has shutdown (no lights) but the sc200 is still running. Closing the web interface and reopening it, I get a communications error on trying to restart the sc4020.

Reading other posts here, I get the impression I may not have used the correct process for shutting the array down. They indicate the correct process should be:

Stop I/O; Shut Storage Center; Switch off sc200 manually. Repeat for 2nd sc4020

Can someone confirm this is the correct process for my configuration please?

This is the first attempt to shutdown after a factory reset and full rebuild,  if that is relevant.

Cheers

Tim