There are several problems with your model which I have fixed. Notice that you have triangulation taking place and this does not work with the
Loop Cut. You need quad topology for it to work. So I deleted the edges with X > Delete Edges.
The other problem is you have duplicate overlapping vertices. How did I know? I selected all vertices with A and then did M > Merge By Distance which removed several thousands (~15k) of duplicate vertices.
After the clean up, I noticed that there is a problem that caused
Bridge Edge Loops to triangulate your faces which will not work with Loop Cuts. It turns out you have too many vertices, $322$ to be exact, at the top most loop instead of $255$ vertices like in the tutorial. The bottom vertices were correct at $255$ vertices.
Another issue is that your top circle is not the proper size, notice that I positioned the 3D cursor at the center of this loop and it should have been aligned with the World Origin. So I deleted the top and bottom loops and repeated the steps starting at @8:20.
Now redoing the steps at @9:47 will work properly without triangulation and Ctrl+R for Loop Cut will now work. Use the scroll forward mouse wheel to add 3 cuts.
I have uploaded the fixed file here: