Cannot add 'Cycles' modifier to F-Curve

I’m new to Blender and I’ve been following this tutorial:

After modeling the mug and animating one 360 degree rotation, the tutorial says to open the F-curve editor and add a “cycles” modifier to make the animation loop. I’ve tried to do this, but I get the following error: Error: Modifier couldn’t be added. See console for details.
I checked the console and saw this: Error: Cannot add ‘Cycles’ modifier to F-Curve, as ‘Cycles’ modifier can only be first in stack.
As far as I know I haven’t added any other modifiers to F-curve. Can someone tell me why this error is occurring and how I can fix it?

nvmnd, The cycles modifier was in fact applied, it just didn’t show anything in the graph. I thought nothing had happened because in the tutorial vid it said that zig zags would appear in the graph. So I tried it again and that’s when I got the error.