In seismic definition,when I press add in next dialogue box of seismic parameters, type tab doesn't show any code. It shows an empty drop down menu. Im using latest staad pro advanced connect edition. The Edition is STAAD Pro Connect Edition V22 update 3
Please try the solution mentioned in the wiki below
https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/43121/staad-pro-connect-edition-has-stopped-working
Although this relates to a software crash but should apply to your situation too.