Here's a video that might help you - https://www.youtube.com/watch?v=QgGcg5uvAyI
Don’t cut it back until all have come back with leaves and then you can tell which will bloom. The blooms come from older stocks. If you cut it back to soon you cut everything off.
What type of Hydrangea? There are so many kinds and they have different ways to get them to flower.
Non blooming hydrangeas may be weather related.
Might possibly be related to your planting zone seasonal conditions. Was your winter spring temperatures quite cold —it’s possible these conditions may have destroyed your blossoms for this season. A different cultivar might be suggested. Please refer to the links below. I hope this helps.
In summer, branches produce new buds for the next spring. These buds stay dormant all winter and bloom in spring. If winter temperatures got too cold, or if there is a spring cold snap that kills the buds, non-reblooming Hydrangea macrophylla will not produce flowers that year.
There are hundreds of bigleaf hydrangea cultivars in
the trade, however, aside from flower type and color, the principal cultivar selection criteria is cold hardiness. Bigleaf hydrangea is rated as a zone 6 to 9 species; however, the shoot system (leaves, stems, and buds) of many cultivars are not hardy in zone 6 (areas west of Roanoke, Virginia), where average minimum tempera- tures for zone 6 are zero to minus10 F. In general, tem- peratures below zero F will kill flower buds as well as well as stems, but new stems may be regenerated from roots the following spring provided that the low winter temperatures did not kill the root system. Flower buds, but not necessarily stems, can be killed in thee range of zero to 10 F.
Hydrangeas bloom on old wood. If you are trimming your bushes all summer long, you are cutting off the blooms for next year. After mine have bloomed in the spring, I will cut back the bush as needed. I will then not trim until the next year. I also sprinkle Azalea food (acid food) on them 3 times a year in the spring (after blooming), summer and fall.
I feed my hydrangeas used coffee grounds year-round. They are also good to use around roses and azaleas.