How do we get the Re-8 code corrected?

An RE-8 Code in the Navy is: Temporary medical conditions or unsatisfactory initial performance and conduct (available to recruits assigned to Recruit Training Command for initial training only). This code could potentially be correct based on that recruit’s specific situation, but the only other code that would fit the situation is RE-3F for PRT failure. An RE-8 code doesn’t permanently disqualify you from trying again, but it does require a waiver from NAVCRUITCOM. That being said, all of that goes through your recruiter or MEPS. Talk to your Recruiter. That Petty Officer or Chief is responsible for guiding you in the process to obtain a waiver and get your code changed.

Your earlier post has you failing bootcamp in 2019 but on this post you failed bootcamp in December 2020. Which is it?

https://www.rallypoint.com/answers/is-there-an-easier-way-to-re-enlist-without-doing-the-pfa

I hope you have trained to complete the quals before returning to do it again. Your CC will take an interest in your success. be prepared to get extra training through Boot if they know about your previous failure. It won't hurt to have it, but it can make your time unpleasant if you are not prepared for it.
I wish you all the success you can muster. your Navy Career will be a time you will learn to cherish for a long time after it's over.