nvram commit
I had that issue for a few weeks until I ran a few commands while troubleshooting something. I'm not sure which of these commands did resolve the issue for me, so give it a try.
Code:nvram unset bwdpi_sig_ver nvram unset bwdpi_rsa_check nvram unset bwdpi_dpi_ver nvram commit service stop_wrs_force service start_wrs
Either it's a mismatch in engine/sig version, or there was a problem with the rsa-signed version of the rules file.
It was the last two - but don't open the QoS tab, you will have to do this again.