Feedparser HTTP conditional GET implementation for pulling only new feed data

I'm trying to pull via Feedparsr only new feed data through HTTP conditional GET implementation, but until now it always return feed2.status=304, even if new contents were pushed through the feed. Here's the code:

import feedparserFEED_URL = 'https://www.giornalelavoce.it/categoria/comuni/settimo-torinese/feed'feed = feedparser.parse(FEED_URL)feed2 = feedparser.parse(FEED_URL, modified=feed.modified)if feed2.status != 304:  for post in feed2.entries:    [...]

I also tried with etag=feed.etag condition instead of modified, but the result was the same.How can I correctly implement it?

Thanks for your time.