My DS is only reception, so I don't have direct experience. However, I noticed that although he has known his letters and numbers since he was 2, he has zero interest in learning to read. We read lots to him and he didn't want to join the words together. I haven't wanted to push him, but remember my brother was similar and refused to read until he was 7 or 8, when he suddenly started reading chapter books as he found a series he liked. Stressed my parents out no end.
As I thought my son might be similar to my DB, 2 weeks ago we signed up for the Reading Eggs and Maths Seeds one moth trial. I was reluctant to, as I don't want to push him and we have avoided any ipad time before. However, he loves it and has made so much progress with both. I have only let him do if for a short time a few times each week and even this seems to show an improvement. Might an online app help?
I looked at lots of options and thought Reading Eggs and Maths Seeds looked like what we needed as my DS is so young, but for older children there seemed to be so many options and some free. Just to help them learn in a fun way and give them a little confidence.
Also, sure you do this anyway, but reading lots of fun books at his reading level or just above to him, to see if he takes to any and starts reading them himself.