When you log into the support portal you should see it in the downloads section.

6MNSI5t3USl76LfpURWGU5u90TIjx.jpg

If you don't see all the version you can contact directly Sencha support to verify if your license have rights for SA 4

If you are just evaluating the Architect, please fill in again the evaluate form https://www.sencha.com/products/extjs/evaluate/ and you will get download link for 4.1 GA. Architect 4.1 GA just came out yesterday. You can try that instead of 4.0.2