The "no convergence" error means that the model cannot iteratinely solve one of the equations. The iterative method knows it is moving further away from the solution (rather than converging on it), so aborts rather than getting stuck in an endless loop.
I don't really know enough to say what equation the model can't solve, but guess that it's something to do the KMT values you've changed. It could be that the bathymetry you've just added has a change that is too sharp, in which case smoothing it may help.
Hope that helps,
Chris