Looking at the OFX file after attempting a One Step Update for all Accounts, have you looked into that file to see if the "missing" Account is included at all? Did they all used to be updated when you did an OSU so this is "new" behavior, or has it always been this way?
"Have not figured out how to capture the OFX file"
Help > Contact Support > Log Files > OFX Log
I'd guess that Account wasn't being included in there as, typically, Direct Connect is very reliable. Glad you got it sorted out.