Thanks IceBreakerSours,
I think the problem came from the inp file since in the new inp file I wanted to add new Dof and I put it in the line
*USER ELEMENT,TYPE=U1,NODES=4,COORDINATES=2,VAR=10
1,2,3
while the standard one is
*USER ELEMENT,TYPE=U1,NODES=4,COORDINATES=2,VAR=10
1,2
Kindly do you know in which part can I add the new Dof in the input file please?
Many thanks and regards,
Msekh