I'm actually quite shocked that neither Apple or anyone else out there in the world knows how to fix this! It's crazy!
I log into iCloud mail and try to add an email recipient to VIP and I get this error message:
I try again later and I get the same error message. I try days later and get the same message. I try several weeks later and get the same message. I try on my iPhone and nothing happens... I don't even get the error message... It just does nothing.
So, all of you brilliant Apple engineers out there designing the best possible user experience... are you listening to your users? This is really important to us and needs to be fixed ASAP, please!