The message "Minimum Curvature did not converge" indicates that the gridding algorithm could not converge with the specified accuracy. This is usually due to overly-tight constraints in the Grid Data - Minimum Curvature - Options dialog. In particular, try increasing the Max Residual and Max Iteration parameters. This condition may be exacerbated by the presence of faults and breaklines. Consider reducing the complexity of the faults and breaklines, if they are in use.
This condition can also result when neighboring data values are extremely different (i.e. orders of magnitude different). This situation is quite rare. Nonetheless, if the minimum curvature gridding algorithm does not converge, even after increasing the Max Residual and Max Iteration parameters by a factor of 10 above their default values, then check your data set for extreme differences. If extreme differences exist, and are correct, then you should consider a different gridding algorithm for your data set.
Updated November 20, 2019