Hydrangeas are not producing flowers, what do I do
Are you pruning them? Do you know what type of hydrangea you have? Some bloom on new wood, some bloom on old wood. Could be other factors too. See if this helps.
See if this site helps you: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm