It is bushy & looks real healthy but hasn’t bloomed this summer. I have it planted in a big well-drained pot in bright sun and water frequently. This is its 2nd summer. I winter it over in our garage. I fed it liquid fertilizer about once a month. It was loaded with blooms last summer. Could it be root bound in the 14″ pot? We live in Iowa, where my summer flowers usually thrive.
Dipladenia need some specific growing conditions to bloom.
These links will help you.