I've never used Bitwarden before, I just went to create an account for the first time and I see this message on both desktop (Librewolf) and mobile (Waterfox) on the signup page. What's BW trying to do here and what mechanism in the browser is blocking it?
Their site might be using some form of analytics or tracking in a script, and could be the error handler on their end leads to a general error pop up like this, but again just a guess on my end