Ok, it seems you are trying to determine variables in steady state that cannot be endogeneously.
- Take inflation: every percentage point higher steady state inflation will increase the steady state nominal interest accordingly. But any consistent combination of both (via the link the Fisher equation provides) is feasible. You need to pin down one of them by setting the value. The model cannot do this for you.
- Take bonds. When Ricardian equivalence holds, bonds and lump sum taxes are perfect substitutes. You cannot tell the model to separately identify both in steady state as only their sum is determined. In contrast, when you fix one in steady state, the other one is also automatically determined.
That is the reason the model is singular when you use the steady state operator.