How does the edge weld connector work in solidworks?

Hello all, I can't seem to get my edge weld connector to function in solidworks. I've looked at several youtube videos and it works for them but I try on my software and it doesn't work. I mess around with the shells and no matter how I change them, I get the error message:
"Invalid edge selected for edge weld. Select a different intersecting edge on Face Set1."
What am I doing wrong? Please help.
I attached a basic assembly of two plates.