i currently changed my whole tank set up from gravel to sand and my 10 inch oscar wont move from his spot or eat ... i know an oscar will sulk for a couple of days when they get a tank change but he hasnt eaten at all... he looks fine but just not eating and he stays in this 1 spot of the tank can anyone give me any suggestions to whats going on? also note that the other 2 oscars that are with him are eating fine and swimming around alot but him

It sounds a bit long to still be sulking, however by changing the substrate you may and upset the balance of the tank and the oscar that isnt eating may be being bullied. Any injuries? Try rearranging the decor in the tank

Another thing you can try different foods like maggots, worms, insects etc

Can you test the water for ammoinia, nitrite and nitrate and post the actual results please

delboy got you covered.
I only had my o stay in one place of the tank for prolongued periods, due to being bullied by my vieja.
After rehoming the vieja, he immediately changed his behaviour.