Feabench Earthquake RSA

Hello,
My model runs the eigenvalues but when trying to run the Earthduake RSA it doesn’t run the eigenmodes and the error is " Factorization of system stiffness matrix failed, the system is kinematically instable." " System Stability Check cannot be executed, the system is ill-conditioned.
→ Please check system masses and/or stiffnesses." The eigenforms don’t show any issues with the model so not sure how to solve it. The COM falls within an atrium, is this the issue?
Thanks