Can't do any sleuthing without any clues! Since they are genetic copies, the "problem" must be environmental (unless it is pathogenic, of which no mention is made). The ball is in your court.

Any pruning been done?

Nope, haven't pruned them at all. They are both in a raised bed on the Southeast side of my house, and are about 8-10 feet apart with an Annabelle Hydrangea and two Night Before Christmas hostas planted between.
Bought them from the same nursery at the same time. Last year they both bloomed.

Other rhan that, I don't know what else I can tell you, nothing has changed.

Linda

If you are wondering about why they aren't blooming, I'll bet they are just going through a growth spurt phase after the first year of establishment. And they will return to blooming. No fertilizer! But if you are wondering about the difference in the two plants:

What about differences between the plants? Soil? Is one near a downspout? I assume you water the Annabelle. Is there a soil grade where one might get more water/fertilizer? Equal sun?

Yours don't seem to be too drastically different - yet. It may be nothing. Now if you're coming over for the swap, I'll show you a similar quandry with a BIG difference.

Rick