No Oven Spring with Ken Forkish's Overnight County Blonde: Help Me Diagnose This Problem

Hello, I've made Ken Forkish's Overnight Country Blonde numerous times, and most of the time, I get an adequate oven spring. There were a few moments—I can count them on my hand, about three—where the oven spring and flavor were out of this world. 

Today's loaf was the first time it was certifiably flat, with nearly zero oven spring.

Here were my steps:

1. Made my levain as usual and let it sit out for about 7 hours.
2. Mixed the dough, folded it every 30 minutes, three times, for about 1.5 hours.
3. Threw it in the fridge for bulk rise. At this point, it was about 1:30 am.
4. The next morning, at about 10 am, I folded it once more and formed it into a ball to proof in a brotform.
5. About 4 hours later, I baked as usual.

Here were the results.

Not only was the oven spring nonexistent, the crumb was also dismal as was the flavor (one dimensional).

I'm guessing I didn't give the dough enough time to do its thing during bulk rise. Indeed, I threw it in the fridge only 1.5 hours after I folded it 3 times, then expected it to be ready for me in the morning at 10 am. While that's a long time to rise, the refrigeration would have dramatically retarded it—it would've either needed more time in the fridge or a few more hours at room temperature.

I want to take advantage of this failure to learn about what not to do in the future!