Antonovka does tend to alternate between fruiting and non-fruiting years, but your situation looks more complicated than that. When all the flowers drop in one year and then don't even form the next year - that's not just a cycle glitch, it's a sign of stress. Usually it happens because of insufficient moisture during a critical period (May-June, when the fruit sets) or sharp humidity fluctuations.
Check two things. First, whether water can pool around the roots - if the soil is dense and clayey, the root collar can rot, which weakens the entire crown. Second, how you're watering: erratically in big amounts, or rarely and a little at a time? Antonovka needs consistent but not excessive moisture. Summer is especially critical - the soil shouldn't dry out to a crust, but it can't be waterlogged either.
For recovery, pay attention to this: stop adding nitrogen (it causes excessive leaf growth instead of flowers), but in late August feed with phosphorus and potassium - that'll prepare the tree for flower bud formation. A mulch layer of 5-7 centimeters under the canopy will also help stabilize moisture. If nothing happens again in spring 2027, then you can start wondering whether it flowers at all or if the problem runs deeper.