WAN Failover Doesn't Seem to Failover

[Ryan2]

I have Untangle (Version: 16.5.2) installed on an edge device (server) with AT&T (primary) and Spectrum (secondary) bridging into the server as WAN interfaces. I had an AT&T outage yesterday, and to my surprise, I lost internet in my house, despite only AT&T being down. I looked at the WAN failover tests report, and only see failures for AT&T, and subsequent success for Spectrum. I also have WAN balancer configured as follows:

External - Spectrum interface 20% of Internet traffic.
External - ATT interface 80% of Internet traffic.

I'm not sure what I'm missing, or why it wouldn't work.