A rowan in the garden 3 doors from me has lots of berries as usual.
I suggest looking closely for signs of pests or disease. Rowan or European mountain ash (Sorbus aucuparia) is susceptible to bacterial fireblight, which makes leaves look scorched, or scab, which can severely defoliate a tree. Check branches for cankers or crown gall. Leaves may show powdery mildew or rust.
Insects such as aphids and scale suck sap from the tree stems and leaves. Borers are the larvae of moths, who bore holes in the stems, causing dieback. Sawfly larvae eat leaves, stems and buds.
Your tree may have expended energy growing new wood and didn't have enough energy left to produce berries this year. It also could be due to poor pollination.
Your tree may need a nutrient boost in the way of fertilization or compost added to the soil.