Arguments are valid if the truth of the premises entails (See: Entailment) the truth of the conclusion.
If the premises are true, then the conclusion can’t be false.
Validity only states that if the premises are true then the conclusion can’t be false, but that doesn’t mean that the premises prove your conclusion to be correct.
E.g.: All humans have tails. Socrates is a human. Therefore Socrates has a tail.
The argument is valid but Premise A is not true, therefore the conclusion may not be true.