Graph Builder connection issues

I’m using SNAP version 7.0.3, in win 10.
I created a graph builder and it worked just fine.
I renamed the folder where I was working and I tried to rerun the graph but I get an error message.
[Nodeid: BandMaths] Could not parse expression: (B8-B4)/(B8+B4). Undefined symbol B8
It seems like the connection, in the SUBSET processor, was lost. I don’t understand why. In the xml file there are all the parameters. Also in the [<node id=“Read”]
I have deleted the the name of the sentinel-2 image.
Please see the attached file

Any help would be greatly appreciated.