Eunice here from Shopify, thanks for posting, and welcome to the Community!
There could be a couple of reasons why your collections aren't showing on your storefront. Let's explore those below:
There is the possibility that your collections aren't set to be available in the Shopify admin. You can check that within the product section here:
Please note the above image shows that this particular example collection has not been added to the store's navigation. While this isn't a necessity to ensure the collection is showing on the storefront, it does make it easier for the customer to find the collection they are looking for via your store's menu. If you haven't already added your collection/s to your navigation, you can learn how to do that here.
Cache and Cookies
Sometimes, when we make changes in the Shopify admin that don't reflect on the storefront it's usually an indicator the browser's cache and cookies need clearing. Browsers can hold onto old information causing issues like this to arise. To fix this I recommend clearing your browser's cache and cookies.
If none of the above fix the issue, please let me know and we can dig a little deeper. It would be great if you could provide the steps you have taken so far to publish your collections on your storefront. Cheers!