When I manage to fix a technical issue that doesn’t seem to be well documented online, I like to share what worked for me. In that spirit:
This morning, as I often do, I emailed an ebook file to my @free.kindle.com address to load it onto my Kindle. For the first time in years, it didn’t work. I got no error message from Amazon, and never got the standard email acknowledging receipt of my file either. The file just never appeared on my Kindle. I tried sending it via their Send to Kindle PC application too, and got the same results – my file disappeared into the ether with no confirmation or error message.
After pulling my hair out for a while, I noticed that my Amazon Cloud Drive (everyone gets 5gb of storage for free) was full. I piled it full of some last resort backup files six months ago and promptly forgot it existed. When I deleted a few files out of that Drive today, suddenly all my Send to Kindle features started working again. I don’t know if this is a policy change or related to the recent changes to the structure of Amazon Cloud Drive, but I do know my Drive has been full for months. I don’t know why it suddenly started rejecting my files, but there we are.
Side note: It’s very poor design for Amazon to not provide any error message in this situation. They could very easily email me about the full Drive, or pop up a message in the PC application. Both options looked like they sent the file successfully. Amazon support was also completely clueless about this when I contacted them.
The TL/DR version: If your @free.kindle.com email address or Send to Kindle program has suddenly stopped working and provides no error messages, check if your Amazon Cloud Drive is full.