What kind of light does it get now?

I have my LL in full but bright shade and it blooms ok in late May or so. The blooms stay green all year though and never switch to white.So some sun like yours is good and will make the green blooms turn white.

However, at the time that paniculatas want to bloom here, that is a time period when we start the 90s regularly so make sure that you (a) do not prune in Spring because some years, like this one, it leafs out very early and will probably bloom earlier than usual too, (b) make sure you have 3-4" of mulch several inches after the drip line and (c) make sure that it has evenly moist soil with no periods of dry, followed by moist and back to dry. This can brown out the leaves and if it browns out leaves, it definitely will kill unopened flower buds or any buds trying to open. Also, some wind protection could be useful in the summer as minor winds can dry the leaves too (although this is more of an issue on big leaf and oakleaf hydrangeas). Generally speaking though, paniculatas do tend to loose some leafage here i the summer months and show their feet.

I already have mopheads and lacecaps going thru the broccoli phase for a month or more. Oakleafs started about a week ago. No signs on the paniculatas though; maybe by mid-to-late May?