Hello, wwicks. I would expect that established paniculatas would be showing flower buds some time between mid-June thru early July since most of them bloom starting in July and they can bloom earlier at times too. Tardiva would be the exception since it is tardy, always.
However, your plant may not be established and could be concentrating on developing a good root system instead. Consider flowers great if you get them on years 1-2. Do not be concerned until years two or three.
I'm a zone warmer than you, have many established Limelights. No buds quite yet. Another week or so. I also sell Limelights, and they bloom in gallon pots. Not to worry, they should get buds very soon.
They've done damage here with one entire bed of hosta Plantaginea and the one Limelight but not the other Limelight just a few feet away. They ate every bud of Splish Splash geraniums and every bud on a low phlox. Forget the roses! They must have been an appetizer since I had exactly one bloom in the back.
From my own experience; Limelight does take time to get established. I purchased mine at blooming age. However, the first summer post transplant. It did skip a season. Once established! Watch out! It's going to be a show stopper! On the hot and humid South weather, it's blooming now. (This one is under dappled shade).