This tells you that the newton algorithm for solving the HFL equation did not converge.
If it just occurs as a warning, but Abaqus reaches convergence (does not stop with an error message) this can be safely ignored.
If it causes Abaqus to actually stop (with Time increment less than or maximum number of cutbacks error message), you need to find out what causes the convergence problems.
This might help (it focuses on mechanical problems, but the logic is the same):
Preprint How to get meaningful and correct results from your finite e...