You might want to place larger size bolts or not standard size bolts.
If bolt sizes exist in the bolt library database *.mdb file but you can not see them or place in your model, review the Hole Diameter sizes specified in general ProSteel Options.
e.g. you have M42 bolt size set in library database *.mdb file. Open ProStructures and go to ProSteel Options (note: set the Expert mode under Dialog settings field ) -> select Files field -> select Hole Diameter -> Text Editor window opens and insert additional row with 42|4 then save text file.
It may be required to reload ProStructures. The M42 diameter bolt should appear in the list now.
The meaning in row is: Number,Metric Diameter | WorkLoose # Imperial Diameter | WorkLoose
Also for bigger diameters please check in the style
the diameter check