If you have run through the Getting Started guide and your shipping rates are not showing at checkout you can use the following points to help resolves the problems.
1. Check your products are marked to require shipping and have a weight assign within your Shopify admin.
2.Check you have a shipping zone setup which includes the areas you wish to service.
3. Add the Sendle Carrier Service to the zones you want the app to cover.
4. Ensure you have linked your Sendle account through your API credentials.
If you have run through these steps and you are still having issues please submit a support ticket and we can help you debug the problem.