Encountered the RuntimeError when solving the PDE

General
1

I have this RuntimeError and I taught it was the mesh which was causing the problem.
What I did was to change the following mesh sizes in GMSH to create different meshes but still had the same error.
size0==0.1
size1==0.01
size2==0.05
size3==0.025
size4==0.5
size5==1
Can someone please help me understand what the error is?

Newton iteration 50: r (abs) = 2.905e-08 (tol = 1.000e-10) r (rel) = 2.984e-05 (tol = 1.000e-06)
Traceback (most recent call last):
File “/Users/bernard/Desktop/working/SEIRD_var-jia.py”, line 162, in
solve(F == 0, u, solver_parameters={“newton_solver”: {“relative_tolerance”: 1e-6}})
File “/Users/bernard/anaconda3/envs/project/lib/python3.8/site-packages/dolfin/fem/solving.py”, line 220, in solve
_solve_varproblem(*args, **kwargs)
File “/Users/bernard/anaconda3/envs/project/lib/python3.8/site-packages/dolfin/fem/solving.py”, line 266, in _solve_varproblem
solver.solve()
RuntimeError:

2

You can increase the maximum number of iterations in your non-linear solver, see:

For further questions, I strongly suggest that you provide a minimal reproducible example.