Dynamic stuff never works for me

hi, I have been following kenji explains videos and none of the dynamic stuff he does with numbers ever works on my excel but everything else does

examples: I was making a live stock portfolio tracker and when I would change which stock I wanted to see, it was supposed to show up on the graph but when I would change it, it would glitch out and not show any stock,

Also I made a chart for a DCF calculation for an expected stock price and the stock numbers were very unrealistic, 

I also am now doing a budgeting forecast and everything was working up until I started to make a dynamic or live forecast and it didnt work again

IDK if this is a settings thing but IDK, can anyone help :)