Hmm, I wish you had identified the two plants by their cultivar (variety) names and-or by the types of hydrangea you have (common types: Big Leaf/French/Hortensia/Macrophylla? Mountain/Serrata? Oakleaf/Quercifolia? Rough Leaf/Aspera, Climbing/Anomala?, Smooth Leaf/Arborescens? Pee Gee/Panicle/Paniculata? Hybrid/Cascading/Other?) and included pictures in order to customize the reply more. Sorry if the response is too long.
The first five types of hydrangeas that I listed typically develop flower buds from mid-summer 2020 to early fall 2020 and these flower buds should open in Spring 2021. The exact time varies based in one’s geographical location: mid-July here in Texas but later if your location is north of me. In very northern areas like Canada, the flower buds can be produced late as in the fall 2020 and open in summer 2021. Knowing that is important because pruning at the wrong time can make you cut off next year’s blooms. The most common reasons for no blooms are due to pruning after the plants have developed flower buds in 2020 or when you experienced very cold weather (or late frosts/freezes) that could have killed the flower buds and the stems. Other common causes: pests like deer, squirrels and bunnies can also eat the flower buds. Sometimes the problem has to do with very dense shade or use of fertilizers that are high in nitrogen. So, fertilize only once in Spring of each year (wait after all danger of late frost has passed) as typically, hydrangeas are not hungry plants like roses are so they require no fertilizer once established… provided that you maintain 7-10 cm of organic mulch past the drip line and provided that your soil is not deficient in nutrients (like when planted in sandy soils) . Note: for Wheatley, your average date of last frost is around the 2nd and 3rd week of April. You can use coffee grounds, liquid seaweed or liquid fish during the growing season but these “minor” fertilizers and all other fertilizers should be discontinued about three months before your average date of first frost. Note: for Wheatley, your average date of first frost is the 3rd to 4th week in October so discontinue all fertilizers by the 3rd or 4th week of July.
The 6th and 7th types of hydrangeas that I listed above are more bloom reliable than the first five as they develop flower buds in spring 2021 through summer 2021 (depends on one’s geographical location) and these flower buds then immediately open. Pruning in the spring/summer when they begin to actively grow could result in cutting off this year’s blooms. But they can often be pruned at any other time. Very dense shade and pests like deer, squirrels and bunnies can be blamed for lack of blooms too.
Unusual types of hydrangeas (involucrata, etc.) can be grouped as part of the first five that I listed.
Note: when I use the term pruning, I am not referring to deadheading of blooms. Deadheading can be done at any time of the year. To safely do it, I either let Mother Nature do it or I cut the peduncle, a string that connects the bloom to the stem/branch.