I’ve found the curve modifier to be very frustrating. I think that you have to get the origins to be at the same location but it can be confusing. From the documentation:
This modifier works in global space, in other words, the actual position of the geometry relative to the curve is determinant to get a correct result.
Typically, you’ll want your object’s origin to be at the center of your geometry (not offset far away from it, you can e.g. Set Origin to Geometry).
And then you’ll want to start with your object’s origin at the same location as your curve object’s origin (you may use snap tools for that…).
Circles and Curve didn’t have the same origin point and scale wasn’t applied…
That’s the problem you don’t always get All the information in these videos… they will click here and it magically works and they forgot to tell you there were 3 other things they did but it got cropped out of the video…