WD SHARESPACE Chassis failure - self-test failure?

I have had a WD SHARESPACE WD20000A4NC from new. It has performed fine with 4 drives set to 2 shares in Mirror mode. Now suddenly I find it is off and when applying power I get all front lights lit & fan spinning for 4 seconds then it turns off. “Feels” like a self-test failure but just a guess. The PSU has been tested with a voltmeter and is delivering 19v as specified.
a) is there any further fault-finding I can perform to get it running again?
b) Does anyone know any independent who can fault-find and fix (since it is now a WD legacy product)
c) Am I correct that if I buy a 2nd hand/refurb chassis and transfer the drives that will not work due to 'MAC Address signing" of the drives (stupid idea if correct)
d) Is there any other way to recover the data on the drives? (It would be nice if I could put them in a different bare NAS Chassis).
Basically, HELP!

Hi @BrianWinn,

Please be informed that WD ShareSpace End of Support:

For more information, please refer to the article WD ShareSpace Online User Guide and Solutions: