NODE SET ASSEMBLY__PICKEDSET HAS NOT BEEN DEFINED - can anyone help?

[Dom10]

Hi people, can anybody help?
I'm quite new to Abaqus..doing some 3 points bending test. When I set penetrator movement as displacement everything works properly but when I place a force to an RP (penetrator is defined as a rigid body) it's constantly popping up the error: NODE SET ASSEMBLY__PICKEDSET35 HAS NOT BEEN DEFINED.
Whatever I did in terms of adjusting/changing in parameters, it's still there.

Cheers

 

[FEA way]

Redefine this node set or manually pick the reference point in load definition. Check all warning messages, they can point you to the actual cause of the problem.