Rockpro64 doesn't boot

[SteveJ]

lsblk looks good:
sdb      8:16   1  29.7G  0 disk
├─sdb1   8:17   1   3.9M  0 part
├─sdb2   8:18   1    64K  0 part
├─sdb3   8:19   1     4M  0 part
├─sdb4   8:20   1     4M  0 part
├─sdb5   8:21   1     4M  0 part
├─sdb6   8:22   1   112M  0 part /media/steve/boot
└─sdb7   8:23   1   1.9G  0 part /media/steve/linux-root

fsck on /dev/sdb6 and /dev/sdb7 shows no errors

But there is no "excitement" when power is applied! No blinking lights on the RJ45 socket when a cable is attached to the router. I'll try the OTG route, but I fear the board may be toast.