All ENx/ethX adapters missing after reboot

A running Ubuntu instance suddenly became unreachable. Reboot same. Appears OK as I can login on serial console, no resource issues. Tried attaching second ENI, still unreachable. Watching console log on reboot I see:

[   10.816067] ena: ENA device version: 0.10
[   10.821183] ena: ENA controller version: 0.0.1 implementation version 1
[   10.829641] cryptd: max_cpu_qlen set to 1000
[   10.831211] ena 0000:00:05.0: LLQ is not supported Fallback to host mode policy.
[   10.932247] AVX2 version of gcm_enc/dec engaged.
[   10.937723] AES CTR mode by8 optimization enabled
[   10.955991] ena 0000:00:05.0: Elastic Network Adapter (ENA) found at mem febf4000, mac addr 0e:d6:48:41:90:95
[   10.975579] ena: ENA device version: 0.10
[   11.018161] ena: ENA controller version: 0.0.1 implementation version 1
[   11.025605] ena 0000:00:06.0: LLQ is not supported Fallback to host mode policy.
[   11.037671] ena 0000:00:06.0: Elastic Network Adapter (ENA) found at mem febf8000, mac addr 0e:38:ab:9f:70:a7
[   11.123572] ena 0000:00:05.0 ens5: renamed from eth0
[   11.141805] ena 0000:00:06.0 ens6: renamed from eth1

but immediately after serial console login, I try ifconfig and get this, no adapters except localhost loopback. Any suggestions??

john@aws-mongodb-sl-1:~$ ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 698  bytes 43567 (43.5 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 698  bytes 43567 (43.5 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0