You might see Cannot POST /SASStoredProcess/do/ when building a SAS Web App on SAS 9. The reason you see this, is that you have an incorrectly defined URL - either the host / server name is incorrect, or you are missing the correct PORT.

For guidance and best practices on building web apps with SAS (Viya or SAS 9), check out https://sasjs.io and the spwa tag on https://sasensei.com.