I used the Reef Flux HD treatment with no recurrences of Valonia (admittedly, this isn't bryopsis) at a quadruple dose; the only thing I can think of from a chemical warfare perspective is to try a higher dose (ensure no carbon/skimming/anything to take the fluconazole out) or you may have a resistant strain/strain that isn't susceptible. FWIW, quadruple the usual dose didn't cause any problems with my tank with the possible exception of being harmful to urchins (anemone, serpent star, Lysmata shrimp, fish, corals including softies/LPS were all fine).
Good luck!