Whispersync doesn't work for my Kindle

Hello everyone!
I'm trying to find a solution to this issue but I'm thinking it could be a problem with amazon servers and not with my device.

I don't know when the problem started but I noticed it after I updated to fw 5.8.1.
Just after the update I noticed that the last read position of the book I was reading was lost and all my highlights as well, I don't remember if I turned on WiFi between the time I purchased this book and the time I did the update.
Then I saw that the highlights and notes from Amazon purchased books did not save to kindle.amazon.com, nor did the last read position or bookmarks synced from my Kindle to my android device.

Basically, my Kindle data does not saves to whispersync but data from whispersync syncs to my device. The new "export notes" option doesn't work either.
If I highlight something on a book with the android app next time my kindle syncs I lose all the bookmarks, highlights and notes that I make on the device.

I'm sorry for my awful english. Do you know of any possible solution I could try?