You could try using Firebug on the Checkout page to see if the AJAX calls are being made and what's being returned. You DO have JavaScript enabled, don't you? It would help if you said exactly what shipping module you're using and exactly how you set it up, so we could tell if you've missed a step. I suggest using just weightquote, since that's the simplest one. Make sure you have weights entered for your products. Turn all other quote methods off and uninstall them (not just deactivate!). Verify the weightquote configuration exists in workflow-ng - delete all configuration from other shipping quote methods that might not have been removed when you uninstalled those modules. Print statements can be inserted to verify that the weightquote module is being called and to see what is returned from the AJAX call. You can inspect your web server logs to see if the AJAX calls are being received. Apparently, the process is breaking down somewhere along the line, and you need to identify where the fault is. Since I know shipping quotes do work, I would expect there is a problem with your installation or with your web host configuration. At the risk of opening another can of worms, have you tried to apply a tax with the uc_tax module (http://www.ubercart.org/docs/user/315/tax_settings)? That also uses AJAX and workflow-ng.