sudden ethernet failure

[Paraplegic Racehorse]

Hardware: Pine64 A64 512MB
OS:  Armbian Buster 20.02.1 (kernel 5.4)

After months of running steady through multiple reboots and sudden power failures, all my boards suddenly lost eth0; all simultaneously; all while powered on and otherwise running without issue. No, I was not logged in and doing things with the system at the time. My router alerted me when the connections dropped out.

Things I tried (and failed):

• different ports on ethernet switch
  
• power cycling (hard reboot)
  
• hook up monitor and keyboard and investigate
  

Investigation discovered no eth0 device. dmesg reports no driver.

lshw is not present on system so I cannot probe hardware and maybe get driver working with modprobe.

So I reflashed the OS and ... no network. dmesg reports no driver.

So I flashed a differnt OS -- Armbian Bionic 20.05.2 (kernel 5.4) -- and ... no network. dmesg output below.

Code:

dwmac-sun8i 1c30000.ethernet: IRQ eth_wake_irq not found
dwmac-sun8i 1c30000.ethernet: IRQ eth_lpi not found
dwmac-sun8i 1c30000.ethernet: PTP uses main clock
dwmac-sun8i 1c30000.ethernet: 1c30000.ethernet supply phy-io not found, using dummy regulator
dwmac-sun8i 1c30000.ethernet: Current syscon value is not the default 2001 (expect 0)
dwmac-sun8i 1c30000.ethernet: No HW DMA feature register supported
dwmac-sun8i 1c30000.ethernet: RX Checksum Offload Engine supported
dwmac-sun8i 1c30000.ethernet: COE Type 2
dwmac-sun8i 1c30000.ethernet: TX Checksum insertion supported
dwmac-sun8i 1c30000.ethernet: Normal descriptors
dwmac-sun8i 1c30000.ethernet: Chain mode enabled
...
dwmac-sun8i 1c30000.ethernet: EMAC reset timeout
dwmac-sun8i 1c30000.ethernet eth0: stmmac_dvr_remove: removing driver
dwmac-sun8i: probe of 1c30000.ethernet failed with error -14

Any ideas or assistance appreciated.