Hi. I now have the new Samsung watch 5. All is good apart from I cant make or receive calls without having my phone on me (so when I leave the house I have to take my phone with me. A bit pointless!) I have a galaxy S21 plus 5G and I have Ver 12. So can't think this would be a reason for it not to work. I've contacted the mobile provider (o2) and they've checked everything and say the settings are OK and samsung say the same (but they will replace my watch but don't think that's the issue as its brand new)
Have you toggled on Remote connection in Watch Setting --> Advanced features --> Remote connection --> Calling?
Also, on your Galaxy phone, in the Settings--> Advance features --> Call & text on other devices - toggle it on.
Needless to say, Watch should be connected to WiFi (connection can take a few seconds to a minute to be established).
I have observed that it can take a couple of retries before the call is successfully established. Your phone and watch need not be on the same WiFi.
Hope this helps.