The filter for Blocked Web Traffic looks for Event Info of "*Blocked URL*", I checked the barracuda web filter connector and "Blocked URL access by..." is the default EventInfo for blocked web access. (We used to use a Barracuda web filter before we were acquired by SolarWinds and this was one of my filters, so I can vouch that at one point it was working... )
If you could give an example of how it is coming through, I can have the team take a look at fixing it, maybe something in a newer firmware caused an issue.