hi, first you should have posted this under the forum topic: Development Discussion -> Blueprint Visual Scripting so it would get exposed to the community in the right place.
other than making sure you set the ‘inventory’ to the correct object type, and that you haven’t changed any names or spelling by choice or accident, then you could try setting that variable to ‘public’ by ‘clicking the eye’ to the right of the variable in the details panel on the left where you created it. (should open the eye)
lots of things have changed since this tutorial was made, so yeah, that could be a part of it. good way to learn tho’
sometimes you just have to think about stuff & try whatever makes sense. look thru the docs & search google and when you fix something like this, you learn a lot by doing so.
edit: needed to add this -> always, always! compile & save if you expect to access any variable you create. if you notice in the video he does this all the time.