I'd been getting this warning on macOS persistently. I am now running Ventura, but I was getting it with Monterey as well. I had tried uninstalling ESET and uninstalling NordVPN (suggested in another post), but that didn't resolve it.
Today I found a Setting, updated the setting and it now appears to be resolved.
Settings>Network>Filters and Proxies>ESET Network Transparent Proxy
was disabled. I enabled it, and now the Web and Email Protection in the ESET app shows functional.
Jleto received kudos from YanaComsecure in Fixed "Web and Email protection is not functional"