I’ve discovered a problem, but I also have a workaround. When accessing my Voicemail from my S21 on WiFi calling, the call will not complete and I can’t even get to the point of putting in my pin. The workaround is to turn off WiFi calling and use cell service. Then I have no issues at all.
However, I had a similar problem with my S8. The call would connect, but when putting in my pin, the call would drop. Again, if I switched to cell service on my S8 there were no issues. So I’m not sure if there is a bigger problem at hand.