Are you sure your NewtonSolver is using you PETSc KSP? Looks like you make and configure the KSP and then do nothing with it.
For example see here, where I design a CustomNewtonSolver inheriting NewtonSolver and configure its underlying linear solver.
Edit: Just saw that you’re using solver in the constructor. And you have ksp_view turned on so you can see that it’s setup correctly. I’m not sure what’s going on without an MWE.