Convergence errors in CHARGE can occur due to different reasons including incorrect settings (e.g. assigned contacts being incorrect, missing materials) or the problem being difficult to solve (e.g. high field mobility model, large simulation region). I recommend looking into our convergence error troubleshooting post for more information.
Here specifically, what stands out is the large size of the simulated device. I recommend recreating a similar device (pn junction with similar geometry) but with smaller size. If the issue persists you need to double check your basic settings like geometries, assigned materials, and boundary conditions.
Otherwise the error is most likely related to the large size of the simulation. In that case adjusting the mesh so that the important features (like doping regions) are appropiately resolved while keeping the number of mesh as small as possible can be helpful.