Then you haven’t received the gift. Perhaps you haven’t received it yet, or perhaps you won’t receive it. “Earnestly desiring” to prophesy obeys the apostolic imperative and pleases our Lord (1 Corinthians 14:1). But he may not be pleased to give you this gift because he’s pleased to give you another gift that is likewise indispensable to the body (1 Corinthians 12:14–31). I know what this is like. I’ve received this gift for others a handful of times in my life, but it’s been rare. Others I know receive this gift much more frequently.
So, ask for it, but don’t force it. Let the sovereign Spirit distribute the gifts as he will, and be content with what you receive.