Rae from Shopify here. Thank you for reaching out about the shipping rates not appearing on your checkout.
We did experience a brief interruption with shipping rates on February 28, 2020. However, our teams quickly fixed this, and this was resolved on February 28th shortly after the interruption occurred.
With this in mind, the shipping rates on your site should be working correctly now, but if you're still experiencing issues with this, feel free to reply to me here with your .myshopify.com URL and I'll be glad to help take a closer look into this. Equally, if there's anything else I can assist with, please let me know.