Custom Curated RSS Feeds plugin – 304 Not Modified

Hi. I managed to create all rss feeds I needed with CCRF and put them all in Blogtrottr (it's a web platform that send emails every time there's a new item published in a rss feed). Today I checked my email and found out I didn't get any message related to all rss feed created with CCRF. I went to check and I saw all feed return a "304 Not Modified" message (but I know feeds in CCRF have been updated). Do you know why or what the problem is? Thanks in advance