RSS feeds require some scripting that might not be present.
Check Store Settings
First, make sure the default RSS feeds are not set to be disabled on your store. Log into your Shift4Shop Online Store Manager and, using the left navigation menu:
Go to Modules.
Search for RSS feeds and click on its + icon to expand the module.
Make sure there is a mark in the Enable RSS Feeds checkbox.
Click Save at the top right.
You might be using an older or modified frame template.
If your automatic RSS feeds are still not showing, you may be using a theme that does not have the necessary coding in the frame.html template. To correct this, go to Settings > Design > Themes & Styles. Then click on the Edit Template button. Select your theme's frame.html file and add the following code to the HTML just before the closing head tag (</head>).
<!--START: FRAME_RSSFEEDS->
<link rel="alternate" type="application/rss+xml" title="Featured Items (RSS 2.0)" href="[store_url]/rss.asp?type=home" />
<link rel="alternate" type="application/rss+xml" title="Products On Sale (RSS 2.0)" href="[store_url]/rss.asp?type=onsale" />
<link rel="alternate" type="application/rss+xml" title="New Releases (RSS 2.0)" href="[store_url]/rss.asp?type=newreleases" />
<link rel="alternate" type="application/rss+xml" title="Best Sellers (RSS 2.0)" href="[store_url]/rss.asp?type=bestsellers" />
<!--END: FRAME_RSSFEEDS->
After saving your changes, the automatic RSS feeds should now be available.
Can I View The Individual Feeds
Yes. If you are using the RSS enabled frame described above, your browser should automatically detect the feeds for display. However, if you'd like to provide direct links to the feeds, you can use the following for reference.
Home Specials
http://[domain]/rss.asp?type=home
On Sale Items
http://[domain]/rss.asp?type=onsale
New Release Items
http://[domain]/rss.asp?type=newreleases
Best Seller Items
http://[domain]/rss.asp?type=bestsellers
Blog postings
http://[domain]/rss.asp?type=blog
Specific Category
http://[domain]/rss.asp?type=category&catid=[catid]
(replace [catid] with the numerical catalog ID of your specific category)