A few possible reasons for your son's difficulty with instructions comes to mind: 1. are the verbal instructions too complex for his age or general language level; 2. does he seem nervous another other stuff, but instructions are places where if you mess up, the consequences are drastic; 3. does he seem to have problems paying attention in other situations.
Situation 1 - some kids have language delays or processing problems that make instructions very difficult for them. If your child is in school, you can talk to his teacher about whether they notice this also. If yes, then it may be a good idea to ask the school to do an evaluation of his language abilities. BUT, sometimes parent (and less often, teachers) give instructions in ways that are too complex or too long. This makes anyone nervous. See if you can cut instructions down to a max of 1-3 steps and see how your kid does.
Situation 2 - directions/instructions are the key to success for tasks. If you child is anxious by nature, this might be the area where that come out the most. Think about whether they seem worried and easily fixated on stuff. When a person is anxious, it often affects their attention.
Situation 3 - some kids have ADHD that makes it hard for them to pay attention to directions that go on for too long. After getting yelled at, they can see the train wrecking coming and can get anxious simply because they almost never get this right. If you see other situations with lots of issues with hyperactivity, a hard time paying attention, then getting an evaluation to check for ADHD might be appropriate.
You will get a report with a series of recommendations....