@kenledger, I’m having almost exactly the same problem since last week! The ONLY difference is that I bake no-knead bread strictly with sourdough.
Last week I prepped a loaf and left it out on the kitchen counter to rise, as usual. When I checked it in the morning I was shocked to see almost NO activity! I waited a couple more hours and there was just a little more rise. I was stymied. Now the weather here in the desert southwest is cooling so my house temperature in the kitchen has reduced but I didn’t think it was a significant enough reduction to seemingly impact my dough as to what I was seeing. Could it be that I have to adjust my dough prep to accommodate the seasonal change in weather? Possibly. I ended up preheating my oven for about a minute or two and then opening the oven door for the temperature to reduce to around 90 degrees or so. I placed my bowl of dough into the oven for a couple hours. That seemed to do the trick (at least for that particular batch of dough) and I was able to successfully bake a tasty viable loaf.
A few days later I attempted to bake another loaf. I prepped it like normal but left it on the counter a few hours longer to account for the cooler kitchen temperature. In the morning that batch of dough was having quite the same issue as the previous loaf! I did the oven trick with that batch of dough and was able to successfully bake a good loaf. But I admit being really stymied as to why this is happening!
Since what I had been feeding my faithful sourdough, named Cyril, hadn’t changed since he was started in February 2018 I’ve had no idea why he wasn’t acting like my happy starter any more.
To add to the frustration I now find myself in total experimentation mode because I can no longer purchase the flour I have been feeding Cyril locally. My local grocery store chains (about 4-5 different chains) are no longer stocking that flour and I had used the last of mine to feed Cyril before my recent bread attempts. Perhaps Cyril is no longer satisfied with what he’s been eating? Maybe he needs a dietary change? He’s kind of forced into one anyway, LOL. So the other day I purchased a new bag of another organic AP flour to feed Cyril with. I’ll have to let you know how he likes it.
Let the experiments begin!