I had this problem and I just solved it. Thought I would post it in case anyone else has the same issue.
I recently posted a scheduled post. It never displayed on feedburner, even though when I checked my feed source, it was there.
I checked plugins, W3 Total Cache settings, pinging feedburner. Nothing was working.
Then I tried re-syncing my feed at feedburner under "troubleshootize" and it came back with error message:
"Your feed filesize is larger than 512K. You need to reduce its size in order for FeedBurner to process it. Tips for controlling feed file size with Blogger can be found in Tech Tips on FeedBurner Forums, our support site."
I thought how could that be. I've always had the same amount of posts going to feedburner and I hadn't increased the size of my posts or too many big pics.
So then I scrolled through my source feed using
That's where I discovered that something really weird happened in one of my posts. The pictures I used had all this garbage text associated with them. I have no idea how that happened. But at least if it ever happens again, I'll know what to do.
I just went into the post and deleted and re-input the photos.
I pinged feedburner.
And like a charm there were all my posts!
Hallelujah! I was trying to figure this out for days.
Hope this helps someone else down the line!