After a steel verification 
, you get the error
Solution
According to EN 1993-1-1 §3.2.1 the yielding strenght fy used during a steel verification, is function of cross-section dimensions. Cross-section with thicker elements (= webs and/or flanges) require a lower yielding strenght than cross-sections with thinner elements. The subdivision for each thickness can be found in Eurocode 3 or in the material library of Diamonds (Note: different subidivisions can apply depending on the national annex.):
As you see in the image above, the maximum thickness equals 150mm (in case of the Belgian NA to Eurocode 3). The error means that your models contains cross-sections for which the dimensions exceed that maximum value defined in the table. Meaning that according to the rules of Eurocode 3, that cross-section cannot be verified.
