clockworkjoe on "[Plugin: Jetpack by WordPress.com] Publicize no longer works"

It seems Publicize no longer works for my wordpress sites - when I try to write a post, it says

Something which should never happen, happened. Sorry about that. If you try again, maybe it will work.

Error code: -10520

https://wordpress.org/plugins/jetpack/

Now I am getting this error when I try to refresh the connection to twitter:

An invalid request was made. This normally means that something intercepted or corrupted the request from your server to the Jetpack Server. Try again and see if it works this time.

Error code: 400