ABAQUS error - 'Node set assembly_left_rp' has not been defined

[Fea_pather]

Hello,

I try to apply a loading on a reference point. But I hit the following error message -

' Node set assembly_left_rp has not been defined'

'A concentrated load has been specified on node set assembly_left_rp . This node set is not active in the model '.

But I have a RP and the a loading has been defined on the RP. How do I resolve this issue?

Many thanks.