Never been able to gain weight, how can I gain through a vegan diet? Advice? : veganfitness

Hey everyone, I’m 24, 5’11 and 138lb (62.5kg). I have a naturally thin body, and no matter how much I eat I can’t seem to gain weight. I’ve eaten my recommended daily calories (circa 2550 + 300 for gains) and not much change. Any advice please?