Hydrangea with no flowers

Lack of bloom is usually due to one of three reasons. Either it did not get enough sun, an early frost or cold spell killed the flowers buds, or it was pruned at the wrong time.

My money is on one of yours either being pruned at the wrong time or an early frost got the flower buds. The plants may be been treated the same but the non-bloomer could well have sat on the outskirts of a sheltered area and been touched by frost or some poorly timed pruning. You say that the non-bloomer is quite vigorous so this has likely happened - no flowers means a bigger plant for next year.

I wouldn't toss the non-bloomer, but rather, put it somewhere sheltered for wintered where it won't get any frost damage or be too cold and then bring it out next season for an even better show.

I was going to ask a similar question myself. I've got two hydrangeas in my (north facing) front garden, they've both been there 10 years plus, and up until last year, both had fantastic blooms every year. I prune them back halfway when the flowers die, and then right back after the worst of the frosts (don't know if this is OK, but has always worked for me both on these, and on previous plants). But last year, and this, the one right by the wall of the house - the most sheltered one - hasn't had a single flower. The other one, somewhat away from the house & therefore getting more sun, has been as good as ever, despite the fact that, certainly this year, it took the brunt of the hard frosts & then was covered in snow for ages. Which seems contrary to what your saying? Strange 

nearer to the house the soil would be drier, perhaps this is what made the difference

I kind've hear what you, and Trillium, are saying, but, why the last two years and never previously? 

I'd agree with MoS - you had a harder winter this year and the one bush just wasn't as hardy as the others possibly due to a drier spot and got more damage from frost. Sometimes not enough food/feeding can also weaken the plant so try mulching with a bit of compost or rotted manure, water well this fall and see what happens next year.

And BTW, pruning right after flowering is really the best and only time for hydrangeas.