Do you have any polysurfaces? They must be single surfaces only.

Please review you are successful in logging into your account (make sure it is a company email and that your account is active).

Review you are uploading the geometry to the correct project. Go to Box #2 "check project", under the current project selected box.

Make sure you have connected all the required building elements from Rhino to the Grasshopper script. Right-click on the component labeled with the appropriate cove.tool geometry category (e.g., Roofs, Floors) and select the "select multiple breps" option. Then, select the corresponding Rhino building geometry. Alternatively, you can select the elements in Rhino and right-click on the component in Grasshopper, then select "Set Multiple Breps." Each type box should say "SUCCESS". If you continue having problems in this section, please review the steps in this article Rhino/Grasshopper Plugin - v.4.2.1 - Workflow for 3D Mode, Daylight, and Energy.

Verify you have no errors or red components in the script. Double-click on these components to troubleshoot and resolve any errors before attempting to export again. Then refresh the web app and select 3d.

After exporting to the geometry page, are you getting kicked back to the first project page? Read this article.