"This site is not secure" certificate error ON only 1 of 2 identical Mirror Gen 2's

I am not unfamiliar with certificate errors. This one warns me and allows me to continue, without any option to save the current state, so it happens every time I want to log in.

BUT it only happens on one of two My Cloud Mirror Gen 2 devices. What could possibly account for the difference? It should not happen differently, if at all of course.

Ideas anyone please?
Thank you!

Hi WillieAT,

Did you try to use another web browser in this concern?

Here, as the My Cloud has not received a WD Trusted Certificate. So accepting the self signed certificate is required to access the My Cloud using MyCloud.com. You should refer below article for more details: