The primary ISP fails but HSRP never moves to the backup router

At 08:10 the whole site loses internet access. R1 (10.10.10.2, priority 110) is the HSRP active router for VLAN 10, virtual IP 10.10.10.1, and uses ISP1. R2 (10.10.10.3, priority 100) uses ISP2, which is working. R1 has preempt and tracks its WAN interface with standby 10 track 1 decrement 20. ISP1 confirms an outage on the router that serves the site, 203.0.113.1. R1's WAN port plugs into ISP1's handoff switch on site, which still has power.