Missing Structural models
Check your version of CADWorx. If you have CADWorx 24 HF1 and the model was made in CADWorx 24 HF5, you may not see the steel. It is never recommended to mix versions within a single project or team. If one person upgrades, everyine should.
Hundreds of errors
If the model opened fine in CADworx 24 HF1 but once upgraded to 24 HF5 it begins having hundreds of errors it is most likely a model version issue which there is a fix. Close the offending model and open a drawing1.dwg. Type CWSUPDATEVERSION at the command line, browse to the folder where the file(s) is, select one or more files and click open. The structural components version will update and all errors will go away. Be cautious though because the fixed files overwrite the original.