I'm a beginner in Lua but I know how to do vector3 and loops. I've came across this problem where i cant do vector3 for models.
https://gyazo.com/7ae360721c197b6c8bef9219bb344860
https://gyazo.com/7b3a160e5ba976bf71b92c3b113dbba7
I am 100% sure that the script is fully working and i have pre-checked to see if there are any faults.
its just lua doesn't like models.

2 comments
You have several problems in there, but the reason you get the error is because "BARRIER" simply doesn't exist in the model.
D= workspace.Shop:WaitForChild("BARRIER")