Are you following up after EVERY SINGLE interview?
Send a thank-you within 24 hours that references specific conversation points and reiterates your interest.
Remind them of a funny moment or similar interests you both discovered during the interview. If you discussed a technical challenge, follow up with a brief solution outline or a relevant article. Show continued engagement with their problems, not just gratitude for their time.
If you were unable to answer a question you know you should have nailed, it's appropriate to provide the correct answer in your follow-up email.
Just make sure you only do this with one question. Persistence with value beats generic politeness.