I've faced this problem once! I set validate method with some conditions like follows:

//...
validate: values => {
const errors: IForm = { //form inputs like username: "" <- empty string
 }
//...

each time I wanted to submit the form, it didn't triggered! so the problem as can be seen above was so simple! the validation is the problem! why?

const errors: IForm | null {username: null} <- it must be null to work correctly