I have been happily using the free trial for my NaNoWriMo prep for the last couple of weeks. Today I tried updating my word count on nanowrimo.org from Scrivener for the first time, and it failed. Eventually I realized that my password manager generated a complex password containing & and @. I changed to a simpler one and the feature started working.
I would imagine there is some over- or under-escaping going on with passwords in this feature.