Does it make a difference if you try http://my.voya.com and let it redirect into https, or go HTTPS directly with https://my.voya.com in the browser URL bar? Also I assume using different browser types (i.e. Firefox vs. Chrome) doesn't make a difference?
There are some firewall drop events that won't generate a usual log entry, to find those run fw ctl zdebug drop then try to access those two sites through the cluster hide NAT.
Next step since you are on R80.10, is to try disabling SecureXL with fwaccel off then try to access the websites again. Be sure to turn SecureXL back on with fwaccel on when done. Not likely to help but worth a try.
There could be a stability/setup problem with your cluster which is why moving it to an arbitrary hide address makes it work, try gracefully powering off the standby member, then see if the reachability of those two websites changes while there is only a "cluster of one".
Failing those, next step as was mentioned earlier is a packet capture using tcpdump.
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