Next year's flower buds form in the summer. If the bush is stressed, by drought, for instance, the buds fail to form or drop off. You could keep an eye on it through the year and water really thoroughly if we have long dry spells. A bit of a feed (I'd use a soluble tomato fertilizer) wouldn't hurt either. Is your soil acid Benkbonk - you don't say where you are - though the fact that next door's Camellia is OK suggests that it is.

Does your Camellia get early morning sun, particularly in winter?

I have several camellias that get browned off flowers Bamboo, but they don't disappear, leaving no trace. I just hope for better luck with the next ones.

if the one on the other side of the fence flowers does it get more sun? is yours in the shade all the time? this may also be a contributing factor.