If you’re keen to have him eating dinner you could remove snacks in the afternoon and move dinner forward. Then he could still have snacks after dinner if he wants

I let them have healthy snacks up to dinner, then only cook a small dinner for them. If they don’t eat it no problem, they’ve already eaten the good stuff I need to get into them.

Try a few different options, give him a few choices (but not too many) perhaps?

Get him to help you make his dinner. I found this works with my 3yr old daughter. It could be as simple as asking him to help you get the ingredients out of the fridge or pantry but it could be enough to make him feel like he’s helped and in turn encourage him to eat his dinner.

Perhaps check the total calories that he is getting. Sometimes even ‘healthy snacks and drinks’ can be giving so much energy that they are mini-meals… (and if the snacks are manufactured this energy is often from sugars and unhealthy fats which would certainly fill him up). Also check that he is moving enough and getting plenty of chance to run around, move, climb etc.

Don’t let him eat too late in the day and if he doesn’t eat dinner then make sure he doesn’t have anything after dinner. He’s soon get the idea that if he’s hungry he will need to eat at dinner time.

Check that there are no snacks after about 3:30, to make sure he is hungry. My MIL told me that she use to reverse lunch and dinner as her three all did the same. So my hubby and his sisters use to have a hot meal(meat n veg) at lunch and were offered sandwhiches at dinner time!

Is maybe his afternoon tea too close to dinner?