Failing a 1st attempt at an AWS certification exam sadly still happens. When we discuss this with students it most often comes down to a lack of appreciation of the nature of the AWS exams leading to a lack of preparation. The AWS exams are well written to ensure that to pass you know your material well.
Don't give up. Now that you know what you are up against, plan to ace it.
Here are some recommendations how how to prepare for the 2nd attempt.
There is a skill to learning.
For the same effort as a bare pass you can become a Guru. The difference is in how you learn. To help you get the most out of your efforts I strongly encourage you to take time to go through the " AWS Certification Exam Prep Guide " by our Mattias Andersson who is one of the few people to score a 100% on an AWS exam.
Understanding the exam
The AWS associate exams are well designed. They focus on testing if you understand the core technology, and if you actually know your stuff. General industry knowledge will not get you through. AWS will not ask you general knowledge questions, and if it looks like they are, they are really asking if you understand how AWS is different.
AWS include questions from all areas of the AWS environment. If you read the exam blueprint, it will not identify any area that is out-of-scope. However ~85% of questions will come from the core topics you have been taught in the course. The remaining ~15% are drawn from what you might call fringe areas. Consider them bonus points if you have taken the time to read a bit further or think a bit deeper about what the white papers and documentation is telling you.
The AWS exams also have a range of question difficulties from simplistic (free marks) to challenging questions. As with the topic scope where there are fringe topics, there are very challenging fringe questions. I am certain that on every associate exam I sat, that I got a question I later saw on a Pro exam. Only one per exam but they were there. The message is that if you want 100% you need to earn it by really knowing your stuff well.
Where we provide them, our 'practice exam' questions are aimed above average, towards the more difficult types. This is to both ensure you are ready, and to lead you to deeper understanding if you want to put the effort in. No apologies, when we introduced the harder questions the pass rate increased and avg pass score jumped by about 10%.
What should I re-study
Be guided by the scoring report you received. Start with area you were worst at and work your way up. Please understand that every exam is different, not just in questions, but also the services and topics covered. Don't focus on the one question or one service you didn't know. You need to work on the whole study area.
Re-study all the core topics as set out in the course. if you really know them you should be able to pass just on the core topics. Know them all and know them well. Read deeper and wider to increase your ability to get extra points. Test your understanding with the practice exam questions. The answers and score are irrelevant. What is important is knowing why every answer is right or wrong (not just that it is). Use the AWS documentation to research every practice answer to find the proof that it is right or wrong. Use the ACG community Forums to talk to other students and alumni to understand wording or why a particular answer is wrong.
Don't expect to master all areas especially of the Pro level. But the more you understand the better your score.
Consider not re-sitting the same exam immediately. Restudying can be hard and boring. Consider doing another course that will help you build a broader foundation or deeper skills in a weak area and then later going back to resit the one you missed.
How do I re-study
My recommendation is to listen to all the lectures again, possibly at higher speed, but do listen. Don't try to memorize material, but seek to understand how the services work and interact with each other. The Moderators who have all completed the exams talk about a 'Mental Model'. When you understand the logic and interaction of the services, the questions become easier to understand and the wrong answers become easier to spot.
The White papers are very important. A number of questions are drawn from them almost word for word. Trying to memorize them will bore you to tears. Instead of "trying to get through them", read them slowly, seeking to understand the use-cases and the anti-cases for each. If something does not make sense, break away to research in the AWS doco to get a better understanding.
When you have idle moments when you cannot be studying, think about a service how it might, or might not be used it to solve problems.
The purpose of the labs is to help you build that mental model of how things go together. Do not just try to memorize the steps, but understand why is each step is needed and how does it go together to create a result.
A technique I found useful was what I call the 30 second summary. For any service or tech, try to be able to talk for 30 seconds on what it is, how it works, how it interacts, and what it is not good at. Developing this will both help you find things to research further, and rehearse recall for when you are in the exam.
Test your knowledge in the Discussion forums. Use every questions as a research topic. Don't 'guess' or 'have an opinion', research it and be able to back you position by reference to vendor documentation.
Finally , unless it is urgent to get the piece of paper, don't rush the exam. There are no bonus points for how soon you do it, but there are bragging rights for how well you do. Many of us advocate studying all three of the associate courses before sitting any exams. That way you get to leverage the breadth of knowledge and repetition of core topics to get higher marks over all.