Anyone else's Nook Simple Touch Kindle app just stop syncing?

I'm running a rooted Nook Simple Touch and the most recent compatible Kindle app (3.2.0.35), as I have been for about three years. Since last week, for no discernible reason, syncing my Kindle library no longer works, i.e. I get the 'Sync failed, please try again later' message, and it therefore no longer receives samples or new purchased ebooks. Also, when searching the Kindle store, the layout of the pages has changed to something that looks distinctly broken, as if CSS has been disabled.

Has anyone else encountered this? Perhaps Amazon have updated their API and broken compatibility with v3.2.0.35 in the process? Or am I the only one who's having this problem – in which case what should I do? I've already tried reinstalling the app, deregistering the device and re-registering, etc...