Had it as well, used the following as a quick fix (reinstall would probably also fix it, haven't tried):
Code Select
curl -sL 'https://raw.githubusercontent.com/opnsense/ports/master/www/squid/files/squid.in' \
| sed 's|%%PREFIX%%|/usr/local|g' \
> /usr/local/etc/rc.d/squid \
&& chmod +x /usr/local/etc/rc.d/squid