Hi, my 7 month old went thru the same thing about 2-3 weeks ago. I've just gone a bit with what he wanted - anything to get him to eat - and also me being persistent with keeping him in the h/chair. I always start him in there, but when he starts grizzling take him out so he doesn't associate the h/chair with getting upset. He's now a lot better after a few weeks of feeding on the floor, bench, outside etc.
Also, I've tried to keep him entertained by placing the chair in different rooms, infront of photos on the fridge, feeding the cats at the same time so he can watch them etc.