XML External Entity Attacks (XXE) : “An error occured!”

I am pentesting XML External Entity Attacks (XXE) in Bwapp, level :low
After capturing the packet in the burpsuit, I added the code in picture

code

on youtube videos it works fine but when i run it : An error occured!
I’m looking for many ways that haven’t been completed yet. Do you have problems like me? If you guys ever successfully fix it, can you help me, thank youuuu