Hi again, 

Thank you for your response. I tried with linear elements without changing the mesh and it did not converge. I then removed the sizing effect and it converged! I am very curious to know why the sizing affects convergence?

The results, however, are off. I am attaching some screenshots to demonstrate that. It seems the material behaviour is captured up until a point where the material starts to behave exponentially. Any suggestions why is that happening?

Note that I am inputting the engineering strains and stresses to calibrate the material model. ANSYS outputs true stresses and strains, so I converted my experimental data to true stresses and strains for postprocessing. 

Thanks again for the support.