McConnell admitted to feeling "pretty raw" immediately after the Olympic race at Izu which was dominated by the Swiss who completed a clean sweep of the podium.
Multiple world and European champion Jolanda Neff took the gold medal in a time of 1hr 15mins 46secs, more than one minute ahead of compatriots Sina Frei and Linda Indergano while McConnell was 28th at 14mins 43secs behind.
"I don't know, I just had no energy, and to be able to finish just felt like the biggest mission ever," said McConnell, a bronze medallist at the past two world championships.
"The conditions weren't that bad actually, it was just not my day.
"(I'm) disappointed that we couldn't do it right, we didn't put any pressure on and tried to do everything normal but I just didn't have anything.
"Third time (at the Olympic Games) and still not putting it together is pretty disappointing."
Reece Homfray