Error: Newton solver did not converge

[dokken]

I suggest you have a look at:

Default absolute tolerance and relative tolerance

I write the following in the context of FE modelling rather than numerical analysis. I.e. this should be interpreted as tips and tricks. Perhaps someone else can contribute something more rigorous, or their own experience. Do you know what to expect the residual of your system to be to machine precision? Adjust your absolute tolerance accordingly. E.g: A Poisson problem with a diffusion coefficient of 1 may yield a residual to machine precision around 10^{-12}. Linear elasticity with a Young’…

Also, to me it seems like your problem is linear and Im not certain that your problem is coercive, see for instance: https://www.math.tamu.edu/~guermond/M610_SPRING_2005/lect3.pdf