Though i am not a child development expert myself, i do understand that speech development is often gender biased. Often girls would develop faster in their speech development than boys do.
Although most kids would be able to speak by 3 years, to speak FLUENTLY is a totally different expectation altogether! I suggest you give him/her a bit more time to develop in this area.
To add on, you can try baby signing. I know your kid is not a baby anymore, but baby signing is not just for babies. Its a workable method that i had tried on my 18 month old girl and it did sped her speech development much faster than other kids her age do. This is just my suggestion. i am sure other parents who tried signing with their kids in the early years would agree with me.