Solution: This turned out to be a flaw in the RAIDXpert2 software. The AMD-RAIDXpert2 User Guide 3.08 dated Jan 2019 par 9.6.2 "Name Arrays" listed some illegal characters in array names that must be avoided. They failed to include the & character. It so happened that I had renamed an array "Data & Documents". That did it!! the GUI goes blank.
The workaround I discovered was to rename the array in the RAID Controller Administrator rcadm with a safe, legal name whereupon the GUI was restored. I have never tested the REAIDXpert2 software since to see if it now elegantly refuses an illegal name.
Sadly, the editors of the Guide have still failed to correct this omission in the latest issue 3.10 dated June 2019 even though I pointed this out months ago. Come on, chaps - get to it!!
Microsoft-certified Desktop Support Technician