So, I'm following this tutorial on YT, and got stuck when trying to add loop cuts inside a circle. What I've done is adding a circle, in Edit mode extruded it inward and merged at centre. Then I need to add circle loop cuts inside this big circle, but the loop cut tool only creates dots. I've tried the inset tool, but it didn't do anything, switching to face mode also didn't help. Also tried to subdivide the mesh, no result.
CtrlR loop-cut and slide navigates its way through a mesh by following quad face-rings.(You can think of it as walking between railway-tracks, and cutting through the sleepers). As it stands, your circle is a fan of triangles. No quads, nowhere to go.
You can fix that by CtrlShiftB bevelling the central vertex with one segment. Now your circle is a face-ring of quads around a central n-gon, and CtrlR will work.